SPEED, VELOCITY, ACCELERATION, & NEWTON STUDY GUIDE - Answer Sheet 1) The acceleration of an object would increase if there was an increase in the A) mass of the object. B) force on the object. C) inertia of the object. D) friction on the object. The acceleration of an object would increase if there was an increase in the force on the object. This is a great example of Newton's Second Law, F=ma. 2) Meghan and Rachel each have bowling balls with the same mass. They both roll them as hard as they can and then measure the speed of each ball. Meghan rolls her ball exactly half as fast as Rachel. How do the forces the two girls applied to their balls differ? A) Rachel used half the force that Meghan did. B) Rachel used twice the force that Meghan did. C) Meghan used twice the force that Rachel did. D) Without knowing the mass of the balls, we can not say. Rachel used twice the force that Meghan did. When mass is equal, force and speed are directly linked, so more force equals more speed. 3) It is almost time for the summer Olympics. The Olympic hammer throw is a throwing event where the object is to throw a heavy metal ball attached to a wire and handle. The name hammer throw comes from an older contest where men threw a sledge hammer. The hammer have different weights, ranging from 16 pounds down to 8 pounds. Imagine there are four hammers to throw: 16, 12, 10, and 8 pounds. If you throw each hammer with the same amount of force, which hammer will move the shortest distance? A) 8 pounds
B) 10 pounds C) 12 pounds D) 16 pounds If the amount of force used to throw each hammer stays the same, then the heaviest hammer, 16 pounds, will move the shortest distance. 4) Sara and Sam went for a two hour walk. According to the graph, between.75 hours and 1.25 hours into their trip, they A) slowed down to a speed of 15km/hour. B) travelled at a constant rate of 30km/hour. C) were not moving since there was no change in position. D) turned around to go home but their speed remained constant. For 30 minutes, Sara and Sam were not moving since there was no change in position. They walked at a constant rate of speed until they reached.75 hours into the trip. At that point, their position did not change for 30 minutes, therefore they were not moving. 5)
John and Caroline go out for a walk one day. This graph represents their distance from home. Which statement accurately describes their walk? A) They walked quickly, then they were still, then they walked slowly. B) They walked forward fast, then they were still, then they walked backwards slow. C) They walked in one direction, then they were still, then they walked in the opposite direction. D) They walked faster and faster until they walked at a constant rate, then they walked slower and slower. They walked in one direction, then they were still, then they walked in the opposite direction. During the first part of the trip, they travel 30 km in 0.75 hours at a constant rate. Then, they are still for 1 hour. Finally, they travel 30 km in 0.75 hours, but in the opposite direction. 6) The graph represents the distance a car travels over time while on the highway. What is the average velocity of the car?
28 A) km hr 50 B) km hr 75 C) km hr 100 D) km hr 75. km hr The easiest place to determine this is the two points (0,0) and (4,300). Over 4 seconds, the distance goes from 0 to 300 km. V = (300-0) = (4-0) 300 4 7) A train engineer started the train from a standstill and sped up to 5 meters per second, she then rounded a corner at a constant speed. She then sped the train up to 10 meters per second on the next straightaway. Next, the train chugged around another bend at 10 m/sec, and then its speed slowed to 5 meters per second after coming out of the bend. Finally, the train reached the station, and the engineer applied the brakes and brought the engine to a stop. How many times did the train accelerate? A) 2 B) 4 C) 5 D) 6 Each time the train changes speed (four times) or direction (two times rounding the turns), it changes velocity, which is the definition of acceleration. The train accelerated 6 times. 8) Mutt and Jeff are running along a path each pushing a cart loaded with rocks. If Mutt's wagon has a mass two times greater than Jeff's and they want to stay together, arriving at their destination at the same time, what must happen? A) Jeff should slow down so Mutt can catch up.
B) Mutt must use half as much force to push his cart. C) Mutt must use twice as much force to push his cart. D) Mutt and Jeff will use the same force, but Mutt will take bigger steps. Mutt must use twice as much force to push his cart. Mutt and Jeff are moving at the same speed. Mutt's cart has double the mass of Jeff's so if he is to stay even with Jeff, according to the formula F=MA, he must use twice as much force as Jeff. The greater the mass, the greater the force, assuming the acceleration is kept constant. 9) Which graph illustrates constant speed and velocity? A) A B) B C) C D) D
Graph D. This is an acceleration graph. Acceleration is the change in velocity. The line is straight which indicates no change in speed or velocity. 10) In baseball, a home run means the batter has hit the baseball into the stands, beyond the baseball field. Compare the force of the batter when bunting the ball into the in-field versus hitting a grand slam. A) There is no way to estimate the batter's force. B) The force is much less when bunting into the in-field. C) The force of the batters in each case is about the same. D) The force of the batter is much less when hitting the ball out of the park. The force is much less when bunting into the in-field. The baseball's mass does not change. In one case, the grand slam, the ball travels a great distance and a high speed. In the other case, the ball travels a short distance at a slower speed. The second case, bunting into the in-field, requires much less force. 11) Assume this is an acceleration graph, where the X axis represents time in seconds and the Y axis represent velocity in m/s. Which statement BEST describes the acceleration represented by the graph? A) There is no acceleration. B) Acceleration is positive. C) Acceleration is positive and constant. D) Acceleration is positive and increasing.
According to the graph, acceleration is positive and increasing. Constant acceleration would be represented by a straight, diagonal line; this line is curved. No acceleration would be represented by a straight horizontal line, a line with no slope. 12) The diagram represents the movement of a train from left to right, with velocity v. Which statement is true? A) The train is speeding up. B) The train is slowing down. C) The train is moving at a constant speed. D) The train is speeding up in certain intervals while decreasing in others. The velocity vector decreased in size. A decrease in the size of the vector corresponds to a decrease in the magnitude of the vector. This means that the correct answer choice isthe train is slowing down. An increase in the size of the vector corresponds to an increase in the magnitude of the vector or speeding up. A constant speed would maintain the size of the vector. 13) Bobby is riding his bike down the road at a speed of 10 miles per hour. Ahead of him, he sees another rider, moving in the same direction. Bobby is catching up with the rider ahead of him. What is the estimated speed of the other rider? A) The same speed as Bobby's. B) Much faster than 10 mph. C) Slower than 10 mph. D) About 5 mph. The other rider must be moving at a speed of slower than 10 mph. Bobby must be riding faster, because he is closing the gap between the riders, even though they are both riding in the same direction. We don't know exactly how fast the other rider is moving, but it must be less than Bobby. 14) Meghan and Rachel each apply the same amount of force to two different bowling balls. Meghan's ball, (ball A), weighs 3 pounds, and Rachel's ball, (ball B) weighs 1 pound. Megan's ball is three times as heavy as Rachel's.
How will the speed of the balls compare? A) Ball B will have three times the speed of ball A. B) Ball A will have three times the speed of ball B. C) Ball A will have roughly the same speed as ball B. D) There is not enough information given for us to know. Ball B will have three times the speed of ball A. Force and mass are indirectly linked to speed. So with the same force, the higher the mass, the lower the speed. 15) Joe is the best baseball player in the world. He can throw a baseball faster than anyone. If the mass of the baseball was increased by 50%, but he applied the same force as he did to a lighter baseball, which of these would best describe Joe's attitude? A) Joe would love to use the new ball in future baseball games. B) Joe would be happy as the new ball would have a faster acceleration. C) Joe would be unhappy as the new ball would have a slower acceleration. D) Joe's attitude would not change as there would be no change in the acceleration. Joe would be unhappy as the new ball would have a slower acceleration. F=MA. If the mass increases and the force remains the same, then the acceleration must decrease. His fastball would be slower! 16) Ben and Jerry went for a walk. They decided to stop for a snack and have some ice cream. How long did they stop at the store to eat ice cream? A) 1/2 hour B) 1 hour C) 1 1/4 hours D) 1 1/2 hours
Ben and Jerry were stopped at the store for 1/2 hour. Check out the section of the line that is flat or horizontal. It runs from.75 hour to 1.25 hours. That is 1/2 hour. 17) The graph shows the speed of a car during a trip along the highway. What can you say, in general, about the speed of the car? A) It is constant during the trip. B) It is moving at a slow rate of speed. C) It is increasing throughout the trip. D) It varies at different times during the trip. It is constant during the trip. The slope of the line is constant. That tells us that the speed is also constant during the trip. 18) Ben helped his parents load boxes and furniture onto the moving truck. He easily carried several boxes out of the house and up a ramp into the truck. Then loaded small pieces of furniture by pushing them up the ramp. Finally, Ben tried to move the refrigerator. He pushed and pushed, but it did not move. Why? A) because the refrigerator was so tall B) because there was no wheels on the refrigerator C) because Ben was tired from moving the boxes and furniture
D) because the refrigerator was much heavier than the other objects It was hard to move the refrigerator because the refrigerator was much heavier than the other objects. It was taller, but a tall object may not be heavier. In this case, the refrigerator was heavier and taller. 19) Newton's second law can be expressed as a mathematical formula for the amount of force needed to accelerate an object. The formula is force equals mass times acceleration, or, F=ma. James is trying to prove Newton's 2nd law of motion. He tries to move four different objects with different masses from point A to point B. The objects are a toy car, a car, a refrigerator and a kitchen table. James finds that it takes the least amount of force to move the A) B) C)
D) James finds that it takes the least amount of force to move the toy car. The toy car has the least mass so it is the easiest to move. 20) Mutt and Jeff are running along a path each pushing a cart loaded with rocks. If Mutt's wagon has a mass two times greater than Jeff's and they want to stay together, arriving at their destination at the same time. In order for them to arrive together, what must happen? A) Jeff should slow down so Mutt can catch up. B) Mutt must use half as much force to push his cart. C) Mutt must use twice as much force to push his cart. D) Mutt and Jeff will use the same force, but Mutt will take bigger steps. Mutt must use twice as much force to push his cart. Mutt and Jeff are moving at the same speed. Mutt's cart has double the mass of Jeff's so if he is to stay even with Jeff, he must use twice as much force as Jeff. The greater the mass, the greater the force, assuming the speed is kept constant. 21) It is almost time for the summer Olympics. The Olympic hammer throw is a throwing event where the object is to throw a heavy metal ball attached to a wire and handle. The name hammer throw comes from an older contest where men threw a sledge hammer. The
hammer have different weights, ranging from 16 pounds down to 8 pounds. Imagine there are four hammers to throw: 16, 12, 10, and 8 pounds. You want to reach the same distance which each hammer. You would need the least force to throw which hammer? A) 8 pounds B) 10 pounds C) 12 pounds D) 16 pounds It would take the least force to throw the hammer that weighed 8 pounds the same distance as the other three hammers. 22) Mike and Mitchell decide to have a foot race. They mark off a stretch of 100 yards, and recruit Cindy to work the stopwatch. After running the race and looking at the results, Cindy declared that Mitchell was the fastest. So how did the boys times compare? A) Mike's time must have been lower. B) Mitchell's time must have been lower. C) Mitchell's time must have been higher. D) The boys had times that matched exactly. Mitchell's time must have been lower. When you cover the same distance in less time than someone else, it means you are moving faster than them. 23) Jane starts driving her car down the road at 30 miles per hour. At the same time, the local train starts going down the tracks. The train is going 35 miles per hour, a little bit faster than Jane's car. After two hours, which will cover the greater distance, the train or the car? A) The car. B) The train. C) The distance they cover will be the same. D) Who travels further is impossible to say. The train. Since the train has a greater speed, and they travel for the same amount of time, the train will travel a greater distance. 24)
Sam and his Dad went grocery shopping. As they went up and down the aisle, adding items to their cart, something changed. The cart got heavier as they added groceries. As the cart became heavier, it also became harder to push. What else MOST LIKELY changed as Sam and his Dad shopped? A) The force of the cart. B) The speed of the cart. C) The size of the cart. D) The direction of the cart. As the cart got heavier and it became harder to push, another thing that changed would be the speed of the cart. 25) Which car is accelerating? A) a car that is unmoving B) a car that rounds a curve at a constant speed C) a car that travels in straight line at a constant speed D) a car that is set to a constant speed of 60 miles per hour A car that rounds a curve at a constant speed is accelerating. Changing direction is accelerating. 26)
Liz puts a 1 kg weight and a 10 kg on identical sleds. She then applies a 10N force to each sled. Which does not explain why the smaller weight accelerate faster? A) The larger mass spends more force overcoming inertia. B) The smaller weight exerts less frictional force to overcome. C) The acceleration depends directly on the mass of the object. D) The motion of the sled relates to action of unbalanced forces. The acceleration depends directly on the mass of the object. This is Newton's 2nd law of motion - F=ma. Rearranging gives a=f/m. So the acceleration depends directly on the force applied and indirectly on the mass of the object. 27) Thomas helps his older brothers, who own a junk yard, on the weekends to earn extra money. He likes to help them push broken-down cars to the back of the junk yard because it makes him feel strong. Last Saturday, they pushed three cars with different weights, and he noticed he used different amounts of force for each one. The cars were the following weights: white car: 2,700 kg red car: 1,500 kg blue car: 2,100 kg Think about how much force is needed to move each car. Which correctly lists the cars in order from the most to least amount of force needed to move them?
A) white, blue, red B) blue, red, white C) red, white, blue D) white, red, blue white, blue, red The heavier an object, the more force is needed to move it. 28) Sam is pushing a cart. How can he make the cart move faster? A) He can add weight to the cart. B) He can push the cart up a ramp. C) He can take the wheels off the cart. D) He can increase the force of his push. Objects can move with a greater speed if a greater force is applied to them. To move the cart faster, Sam can increase the force of his push. 29)
A dog named Rascal leaves his home and travels a short distance and then returns home. The graph shows his position as a function of time. How does his velocity on his return trip compare to his velocity for the first 5 seconds? A) His velocity was slower when compared to the first 5 seconds. B) His velocity was positive on the return trip when compared to the first 5 seconds. C) His velocity on the return trip was twice as slow when compared to the first 5 seconds. D) His velocity on the return trip was twice as fast when compared to the first 5 seconds. His velocity on the return trip was twice as fast when compared to the first 5 seconds. Remember, velocity is the change in position divided by the change in time. The return trip has a velocity of 2 m/s (in the opposite direction, so it could be referred to as -2 m/s) compared to the 1 m/s velocity of the first 5 seconds. 30) A car's position in relation to time is plotted on the graph. What is the car's average velocity?
A) 5 m/s B) 10 m/s C) 30 m/s D) 50 m/s 10 m/s The car's average velocity is calculated by taking the difference in two positions divided by the difference in their respective times. For example, in this case, (20 m - 10 m)/(2 s - 1 s) = 10 m/1 s = 10 m/s 31) Why does an object in motion stay in motion unless acted on by an unbalanced force? A) because forces are what stop and start motion B) because balanced forces can not exist in nature C) because motion is the inherent state of all matter D) because motion, once begun, continues to accelerate An object in motion stays in motion because forces are what stop and start motion. No movement can begin without a force to start it. This is inertia, Newton's First Law. 32) A train rolls to a stop along a horizontal track without the conductor applying the brakes. What answer choice BEST explains why this occurred? A) The train ran out of momentum. B) The opposing force of friction stopped the train. C) The natural state of the train is not to be in motion. D) The force of gravity slowed the train until it stopped. The train rolled to a stop because the opposing force of friction stopped the train. If the track had been frictionless, it would have continued without stopping or even slowing. 33) The image above shows two opposite forces acting on a rolling cart, what can we say is true about the affect of the forces on the cart? A) It cannot be determined without knowing which man is stronger.
B) It cannot be determined because one man is taller than the other. C) The forces are unbalanced, and net force on the cart moves it to the left. D) The forces are unbalanced, and net force on the cart moves it to the right. The forces are unbalanced, and net force on the cart moves it to the right. Opposite unequal forces equals motion in the direction of the net force. Net force is 25 Newtons to the right, so the cart moves right. 34) Your teacher was given an apple by a student trying to get on her good side. It sits on her desk the whole year, not moving. You know that, if the apple were to roll off the desk, it would fall to the ground. So what is keeping the apple motionless on the desk? A) Once placed on the desk, gravity is no longer acting on the apple. B) The downward force of gravity on the apple is balanced by a larger force on the apple by the desk. C) The downward force of gravity on the apple is balanced by an equal but opposite force on the apple by the desk. D) The downward force of gravity on the apple is balanced by an equal but opposite force on the apple by the teacher. The downward force of gravity on the apple is balanced by an equal but opposite force on the apple by the desk. Since the apple is not moving, you know that equal but opposite forces are balanced. 35) Forces that are equal in strength and opposite in direction are A) balanced forces. B) unbalanced forces. C) always result in motion. D) always the result of motion. Balanced forces are equal in strength but opposite in direction. 36) According to the diagram, the block should be moving in which direction? A) The block should not move at all. B) The block should move to the left. C) The block should move to the right. D) There is no way to tell which way the block should move. The two forces applied are n ot balanced. The block should move in the direction of the larger force. So, the block should move to the left. 37) Which example best represents an object with balanced forces acting upon it?
A) A boat moving through the water. B) A book sitting on a high shelf. C) A wagon rolling down a steep hill. D) A baseball thrown thrown in the air. A book sitting on a high shelf best represents an object with balanced forces acting upon it. 38) Veronica and her little sister, Monique, are playing on a seesaw. If Veronica weighs 75 pounds, and Monique weighs 60 pounds, which statement is true? A) If they push back and forth for a long time, the seesaw will begin to move on its own through gravity. B) If they both push off the ground with equal force, the seesaw will balance and their heights would be level. C) To lift herself from the ground, Monique will need to push much harder than Veronica because she is lighter. D) If they stop adding force to make the seesaw move, Monique will be in the air and Veronica will be touching the ground. If they stop adding force to make the seesaw move, Monique will be in the air and Veronica will be touching the ground. The heavier person would force the seesaw down. 39) Using two spring scales, students pull on opposite sides of a dynamic cart at rest. 5 Newtons of force is pulling left and 5 newtons force is pulling right. Describe the motion of the cart? A) The cart will move to the right. B) The cart will move to the left. C) The cart will not move. D) The cart will move up. With equal forces left and right, the net force is zero. The cart will not move. 40) An object in motion will stay in motion unless acted upon by what type of force? A) balanced B) electrical C) magnetic
D) unbalanced unbalanced Unbalanced forces are the only type that will change an object's motion every time. Electrical and magnetic forces would only change the motion of some objects, and a balanced force does not change motion.