Friday, April 9 Asynchronous Learning Activity

READ ME Potential energy is stored energy. The gravitational type of potential energy comes into play when objects have a height. The higher off the ground an object is, the more potential energy it has.As the object goes down, it picks up speed and therefore more kinetic energy. Sometimes heat is involved, especially when two things are rubbing together. This is thermal energy.To find gravitational potential energy, I need to know about distance (height) and mass. To find kinetic energy, I need to know about speed (velocity) and mass. Question 1:A girl who is riding her bike coasts down a hill without pedaling. As she goes down the hill the bike speeds up and the tires get a little warmer. What energy transformations are occurring? Kinetic energy is transformed into gravitational potential energy and thermal energy. Gravitational potential energy is transformed into kinetic energy and thermal energy. Gravitational energy is only transformed into kinetic energy. READ ME As objects go down a hill, their potential energy turns into kinetic energy. However, when they go back up the hill, their kinetic energy turns back into potential energy as they slow down. In order to make it over a hill, the object must have MORE kinetic energy than what it started with. QUESTION 2: Will the ball make it over the hill? Yes, because the ball will build up enough energy on the steep part of the track to make it over the hill. Yes, because the ball gains energy the entire time it is moving, so it will have enough energy to go over the hill. No, because the total amount of energy in the system remains the same, which means that the ball cannot go any higher than the point which it started from. READ ME! The law of conservation of energy states that energy cannot be created or destroyed. It can only change form or go "somewhere else". On Earth, air resistance slows objects down. The kinetic energy is not lost, it is transferred to the air. Question 3: Why does the ball stop swinging? The kinetic energy of the ball is transferred somewhere else, like the air, as the ball swings from side to side. A little bit of the ball’s kinetic energy is used up each time it swings from side to side, but the motion energy is not transferred anywhere else. Some kinetic energy is transferred somewhere else, like the air, and some motion energy is used up. READ ME! Power equals the force x distance of an object divided by time. If I am trying to solve for time, I multiply force x distance and then divide by time. QUESTION 4: A winch is a hauling or lifting device consisting of a rope, cable, or chain winding around a horizontal rotating drum, turned by a crank or by motor.The maximum power output of an electric motor on a winch is 8000 watts. How long will it take the winch motor to pull an 800 N load a distance of 80 m? 8 seconds 0.008 seconds 800 seconds Question 5: The gravitational potential energy of an object depends on which of the following? Both the speed of the object and the object’s distance from the center of the earth. The speed of the object but not the object’s distance from the center of the earth. The object’s distance from the center of the earth but not the speed of the object. Question 6: Two students are running in a race. Student 1 has more kinetic energy than Student 2. Does Student 1 weigh more than, less than, or the same as Student 2? Student 1 weighs more than Student 2. Student 1 weighs less than Student 2. Student 1 weighs the same as Student 2 The only way to know which student weighs more is to also know how fast each student is running. READ THIS! To find gravitational potential energy, we multiply mass x gravity x height. Question 8a. A girl has a mass of 45 kg. She is on top of a 15 m tall hill. Gravity (g)= 9.8. Find her gravitational potential energy. 675 J 33000 J 147 J 6600 J 8B.Work = force x distance. If friction has a force of -25 N and the girl moves a distance of 75 meters, how much work is friction doing? +1900 J -1900 J +375 J -375 J 12. Work = mass x acceleration x distance: What is the rate at which work is done in lifting a 35-kilogram object vertically at a constant speed of 5.0 meters per second? Acceleration due to gravity is 9.8. 1700 J 340 J 180 J 7 J Acceleration = weight divided by mass14.On the surface of planet X, a body with a mass of 10 kilograms weighs 40 newtons. The magnitude of the acceleration due to gravity on the surface of planet X is _. 4.0 × 10^3 m 4.0 × 10^3 m 9.8 m 4 m