Science 10 Physics (Mechanical) Kinetic Energy What is Kinetic Energy? How do we describe motion? (watch the video clip and describe the motion you see) What gives an object MORE kinetic energy? (If a lacrosse player were to run into you, what factors would make it hurt more?) Calculating Velocity Velocity and Speed are measurements of how fast an object is moving. In Science 10 we will use these two terms interchangeably, but be aware that there is a difference. Velocity is a vector in that it has both speed and direction. Energy isn t directional, so we are really only concerned about the speed at this point, not the direction. In groups of 2-3, figure the average velocities of the battery powered cars (red and blue). What information do you need to figure out how fast they are going?
Calculating Velocity The formula: Examples: Velocity: It takes a sprinter 8 seconds to run forward 75 meters. What is the sprinter s average velocity? Distance: What distance is covered by a skateboarder who travels 3 m/s for 12 s? Time: If a cyclist travels forward at 12 m/s, how long would it take for the cyclist to travel 600 m? Try On Your Own: 1. What is the average velocity of a dog that runs 35 m in 4 s?
2. If a baseball is thrown at 25 m/s toward home plate, what distance did the ball travel after 0.65 s? 3. Two friends want to paddle their canoe 450 m across a lake. If they head across the lake at 2 m/s, how long does it take them to cross? 4. What is the average velocity of a snail that crawls 0.2 m forward in 150 s? 5. If a kayak has an average velocity of 2 m/s, how far has it gone after 35 s? 6. If sound travels at 350 m/s, how long does it take the sound to travel 110 m across a field? 7. How long does it take to run forward 5 km if the runner s forward velocity is 11 km/h? BONUS convert the answer above from hours to seconds.
Calculating Kinetic Energy Formula: Examples: 1) A 60 kg student is running with a velocity of 2 m/s. What is the kinetic energy of the student? 2) A 0.6 kg basketball is flying through the air at 8 m/s. What is the baseketball s kinetic energy? 3) A 1500 kg car is driving down the street at 50 km/h, what is the car s kinetic energy? 4) Who has more Kinetic Energy? Explain why for each scenario. a. A 50 kg dancer running across the stage, or the same dancer walking across the stage? b. A grade 10 HWSS student skateboarding across the parking lot at 15 km/h, or a 300 kg sumo wrestler skateboarding across the parking lot at 15 km/h? c. An airplane at lift-off or a helicopter at lift-off? 5) What has a greater effect on the amount of kinetic energy that a moving object has, the mass or the velocity? Explain.
Kinetic Energy Practice Worksheet 1) A 3 kg ewok is travelling at a constant speed of 7 m/s. What is its kinetic energy? 2) A 1 kg lightsaber is moving at 8 m/s. What is its kinetic energy? 3) A 122 kg wookie jumps off a cliff, after 4 s the wookie is falling at 44 m/s, what is the wookie s kinetic energy? 4) An 8 kg bantha poodoo is dropped from a height of 7 m. When it hits the ground it is travelling at 11 m/s, what is the kinetic energy of the poodoo just before it hits the ground? 5) A 1400 kg podracer is flying at 150 km/h. What is the podracer s kinetic energy?
Kinetic Energy Challenge Questions 6) How fast is a 70 kg Jedi running if they have 400 J of kinetic energy? 7) A 9 kg object falls off a 2 m high shelf. a. If all of the objects potential energy is converted into kinetic energy just before it hits the floor, how much kinetic energy will it gain? b. How fast is it moving? 8) A golfer wishes to improve her driving distance. Which would have more effect? Explain. a. Doubling the mass of the golf club OR b. Doubling the speed with which the clubhead strikes the ball?