![]() Since there are two point charges, the total potential will just be the sum of the two potentials. Where k is the Coulomb constant ( and r is the distance from the point charge to the final location. Since I am dealing with two point charges, I can use the following expression for the potential due to a point charge (with respect to infinity): Yes, you could also calculate the work needed to move the charge-I’ll do that also. That means I just need to calculate the change in electric potential from infinity to point B. The energy needed would be equal to the change in electric potential energy which is equal to: Let’s start with the energy to bring an electron to point B. But let’s just start with a problem and then solve it in more ways than you wanted. This connection between the electric potential (change in electric potential) and the electric field can get sort of crazy. Describe the energy transformations that you observe during the motion of a pendulum.I’ll be honest. How high would you have to lift a 2000 kg car to give it a potential energy of: (a) 4.0 × 1 0 3 J (b) 5.00 × 1 0 5 J ? 25. (a) What was the total kinetic energy before accelerating? (b) What was the total kinetic energy after accelerating? (c) How much work was done to increase the kinetic energy of the bicyclist? 24. A 50.0 kg bicyclist on a 10.0 kg bicycle speeds up from 5.00 m / s to 10.0 m / s. (b) when it hits the bystander on the head,Ģ. If the mass of the coconut is 1.5 kg, calculate the potential energy of the coconut relative to the ground at each of the following sites: (a) while it is still in the tree, (c) when it bounces up to its maximum height, (e) when it rolls into a groundhog hole, and falls 2 m to the bottom of the hole. It bounces back up 1 m before falling to the ground. ![]() A coconut falls out of a tree 10 m above the ground and hits a bystander 2.00 m tall on the top of the head. How fast must a 400 kg motorbike be moving to have a kinetic energy of: (a) 1, 200 J (b) 1, 600 J ? 22. Calculate the kinetic energy of a 2 Kilogram cannon ball travelling at: (a) 50 m / s, (b) 45 m / s, (c) 92 m / s. What is the plane's loss of potential energy? 20. A 2 × 1 0 4 kg airplane lands, descending a vertical distance of 11.0 km while travelling 120 km measured along the ground. What is the gravitational potential energy of a 70 kg person standing on the roof of a 12 -story building relative to (a) the tenth floor, (b) the sixth floor, (c) the first floor? (Each story is 2.80 m high.) 19. Part II Kinetic Energy and Potential Energy. How long would it take a 600 W electric motor to do 17, 500 J of work? A power mower does 8 × 1 0 4 J of work in 0.4 h. How much electrical energy (in KWh ) would a 120 W light bulb use in 34 days if left on steadily? 16. a) What is the initial Gravitational Potential Energy of the Ball at the top of the incline? b) What will be the final Kinetic energy of the ball at the bottom right side of the incline? c) If there were friction between the ball and the incline, what would happen to the final Kinetic energy of the ball at the bottom of the incline? Increase, decrease, or states the same? 15. A 0.3 Kg ball is initially at rest at the top left side of a frictionless incline plane: The incline is 0.25 m height and has a length of 0.65 m. A 100 watt light bulb runs for 120 seconds. You use 40 J of energy to rise a 250 N object. How much work was done? How much power did you spend? 12. You push down on a 4.0 N box against the floor for 2 minutes. ![]() How much work was done? How much power did you used. N bag of potatoes up a 5.0 m flight of stairs in 26 seconds. How much power does it take to lift 50.0 kg 8.0 m high in 4.00 s ? 10. How much power does it take to lift 40.0 N 11.0 m high in 6 s ? 9. A 90.0 kg man pushes on a 5.0 × 1 0 6 ton wall for 350 s but it does not move. How much work is this if the force of friction acting on the sliding box is (a) 100 N, (b) 250. A boy pushes his little brother in a box with a force of 500 N for 324 m. If a small motor does 200 J of work to move a toy 17 m, what force does it exert? 6. How much work is it to lift a 25 kg sack of cement vertically 4.3 m ? 5. Calculate the force needed to do 500 J of work while pulling a cart a distance of 3.4 m. Calculate the work done by a 40 N force pushing a 0.5 kg toy 2.3 m. Calculate the work done by a 50 N force pushing a cube 0.25 m.
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