AP/IB Physics         The Bowling Ball Lab

Conservation of Energy and Conservative Forces

Introduction

In conservative systems, the total work depends only on the coordinates of the object. Thus, no energy is used in doing work by non-conservative forces, such as friction. In this lab, the kinematics of motion and the total energy of a system are studied, and the changes that occur in KE and Ug are examined.

Materials

building (roof), bowling ball, ping pong ball, several stop watches, measuring tape

Procedures

1. Mr. S will throw the bowling ball off the roof of the school horizontally. Record the time of fall with several stopwatches; drop the low and high recordings, then take the average.

2. Determine the horizontal distance the ball landed from the building.

3. Repeat the throw with another type of ball and collect the same data.

Results and Discussion

From your data,

1. using kinematic equations, calculate height from which the ball was thrown, and the horizontal and vertical components of the ball's velocity.

2. determine the maximum velocity of the ball and the angle from the horizontal as it hit the ground.

3. determine the Ug, KE, and ME of the ball at the time of launch (t = 0 s).

4. plot a graph of Energy (J) vs. distance fallen (m) for the potential, kinetic, and total energies of the ball from t = 0 until it hits the ground.

5. plot a graph of Energy (J) vs time for the potential and kinetic energies of the ball from t = 0 until it hits the ground. Explain the shape of the KE curve.

6. From the maximum KE on your graph, calculate the maximum velocity and compare with your calculations from (2) above.

7. Does total ME = KE + Ug throughout the fall? Are any non-conservative forces present that you can detect? How would you know if they were present? Compare the data from the ping pong ball throw. What differences are there? Explain.

8. Calculate the slope of the KE line from the graph of J vs. m. What does the slope represent? Compare with what was given.

9. Draw a tangent to the KE curve in the graph from (5) somewhere between 0.5 and 1.0s. Calculate the slope. What does this slope represent?

10. Starting with KE = 1/2mv2, and using the kinematic equations, Newton's Second Law, and the work equations, prove that KE = W (work-energy theorem).