The amount of matter in an object.

Transcription

1 Definitions: Mass: Weight: Gravity: Resistance: Opposing The amount of matter in an object. The measure of the pull of gravity between an object and the Earth. A force that acts pulls objects together. Depends on how much mass is in an object. ( stronger pull if more mass. Weaker pull if less mass) AND how far apart objects are( Closer= strong pull/ farther=weaker pull) Anything that pushes back against motion. Air resistance and water resistance are examples. Means opposite in direction Balanced Force Unbalanced Force ** Up thrust was omitted Forces that cancel each other out. Force is equal in size and opposite in direction. You sit on a chair. Gravity pulls you down, the force of the chair pushes you up. Forces that are not equal and cause a change of motion. You move in the direction of the greater force. Ex. Dogs playing tug of war p ) How could you make a sheet of paper fall as quickly as possible? A Cut the paper B Crumple it into a ball Why? By crumpling the paper up, it reduces the surface area. Less air pushes up stopping it from falling. It falls quicker. Less surface area= less air resistance.

2 2) When an object falls, air resistance does what? A Pushes up as the object falls B Pushes the object down faster Explain: Gravity is pulling the object down toward the center of the Earth. Air is in the way and pushes up on the object slowing it down. 3) Weight is a force and is measured what? A grams B inches C Newons 4) Where would you feel the heaviest on the moon or on Earth and Why? You would feel heaviest on the Earth because the Earth is larger and has more gravity. There is a stronger pull on the Earth than on the moon. Mrs. Darmanin would rather use a scale on the moon than on Earth! 5) Which of the following is true and why? A B C Gravity only acts through air, not water or land. Gravity doesn t act on airplanes flying in the sky. Gravity always acts toward the center of the Earth through air, land, and water. 6) If gravity pulls you towards the center of the Earth, why don t you fall through the pavement? The pavement provides an upthrust or upward force holding you up on the surface. 7) What has more force? A An apple falling in water B An apple falling in air Why: Water is denser than air and has more upthrust or upward push. The apple will fall slower in the water than in the air. 8 What is not a force? A Friction B Weight C Height

3 Read each statement. Write true if the statement is true and false if the statement is false. A moving object continues to move until a force stops it. True A moving object eventually runs out of force and slows down. False, Remember Inertia, an object doesn t run-out of force, it will keep moving until a force acts on it. A moving object travels in a line until a force changes its direction. True 10) When an object is at rest or stationary what kind of forces are acting on it? A Balanced Forces B Unbalanced Forces Why? Even though the object is not moving, there are still forces acting on it, but they are balanced. The forces cancel each other out and the object doesn t move. There is a force equal in size or strength pushing the object down and one the same size equal in size or strength pushing it up. (Or think of a tug of war. The rope doesn t move if both sizes have equal forces. The forces are balanced 11) What is a good way to slow down on a bicycle? A Drag your feet along the ground B C Pedal faster. Ask someone to give you a push. Explain your answer: When you drag your feet the two objects touch creating friction which will stop motion. 12) What is a good way to speed up on a slide? A Hold onto the sides of the slide B Wear slippery clothes Explain your answer: The smoother your clothes the quicker you will slide because there will be less friction. 13) Pushes and pulls of examples of A Forces B Stretches C Twists

4 14) When you push a toy car, it eventually stops. What causes it to stop? A Friction B Gravity C Twisting Explain your answer: Both friction and gravity. Gravity is always acting on an object pulling it down onto the surface. When the wheels rub along the ground, eventually friction occurs and stops the car. 15) With the same push, would a heavy car travel further or less far than a light car? A Further B Less Far C They d both travel the same distance Explain your answer: The more mass, the stronger the push needs to be in order to move the car. If you use the same strength push, the car won t go as far. 16) On what type of track would a sled move the fastest? A A flat track B A gently sloping track C A steeply sloping track Explain your answer: When the car is lifted up it increases the gravitational pull. The sled will come down the track the fastest. Think of what happened when we raised the gradient of the truck. 17) What else might affect the speed of the sled moving down the track? A The color of the track B The surface of the track C The name of the track Explain your answer: Think of the surface of the track. The smoother the track (ice or vinyl) the car moved quicker. When the car was on carpet it moved slower. Friction between the surface affects the speed of the sled.

5 Name Date BBC Forces in Action Video Clip Factors that have an effect on motion:,,,, Your Guess: We are going to release the truck. Guess where it will stop. Truck alone Your Guess Actual Truck alone Small Small Large Large Small Weight Small Weight Large Weight Large Weight

6 What did I learn: