Potential/Kinetic Energy Questions

Question

1. Greg raises a 75.0 N physics book from a table 0.750 m above the floor to a shelf, 2.15 m above the floor. What was the change in potential energy?
2. A bowling ball, travelling at 0.950 m/s comes to a stop, has 4.50 J of kinetic energy. What is its mass?

Answer 1

1. If the table were suddenly whipped from underneath the book, one would see a 75-Newton Force driving through a Distance of 0.750 Meters, which gives an Initial Potential (or Stored) Energy of

(75 Newtons) Times (0.750 Meters) or 56.25 Joules.

At 2.15 Meters over the floor, the Potential Energy of the book would then be (75 Newtons) Times

(2.15 Meters) or 161.25 Joules.

The Change In Potential Energy is then given by (161.25 − 56.25) Joules or 105 Joules.

2. Equate Kinetic (or Active) Energy to (0.5)(Mass)(Velocity-Squared) or (4.5 Joules) =

(0.5)(M Kilograms)(0.95 Meters Per Second)² which reduces to M Kilograms equal

to (4.5÷0.5÷0.95÷0.95) or 9.972299169 Kilograms (equivalent to 9.972 Kilograms).