TECHNOLOGY-BASED LAB ACTIVITIES

Chapter
5
HOLT PHYSICS
Technology Lab
Loss of Mechanical Energy
OBJECTIVES
• Measure the change in
the kinetic and potential
energy as a ball moves
up and down in free fall.
• Graph potential energy,
kinetic energy, and total
energy.
• Analyze the graph to
determine how much
kinetic energy is lost.
• Reach conclusions
regarding the amount of
energy possessed by the
volleyball as it fell in the
neighbor’s driveway.
MATERIALS
✔ graphing calculator with
link cable
✔ CBL system
✔ PHYSICS application
loaded in calculator
✔ Vernier motion detector
✔ wire basket
✔ volleyball or other ball
The Case of the ’65 Mustang
One day, as you are playing volleyball with a group of friends in your driveway, a
stray serve accidentally goes over the fence to the neighbor’s driveway. When you
go to retrieve the volleyball, your neighbor points out a dent in the roof of his
classic 1965 Mustang, claiming that the volleyball hit the car. You apologize to
your neighbor for the ball going over the fence, but explain that you know the
volleyball didn’t hit the car because you heard it land on the pavement.
The next day, the neighbor presents you with an $1800 repair bill. Not wanting
the dispute to get out of hand, you suggest turning to the local neighborhood
organization for arbitration. Your neighbor agrees, and within a week the
president of the organization contacts you. Your neighbor has already presented
his case to the president, using the following:
• A passage from a physics textbook stating that mechanical energy is conserved
during projectile motion, even though it may be converted from
kinetic energy to potential energy and back to kinetic energy again.
• Calculations estimating that the ball left the server’s hand (about 1.5 m in
height) with an initial vertical velocity component of 8.29 m/s, rose to a
height of 5 m (passing just under the overhanging branches of a tree), and
hit the roof of the car (also at 1.5 m) with a downward velocity of 8.29 m/s.
• Calculations showing that, based on a ball mass of 0.5 kg and an impact
velocity of 8.29 m/s, the kinetic energy of the ball at the time of impact was
19.58 J.
• Testimony by a materials engineer that any impact by an object with kinetic
energy greater than 18 J could dent the roof of the Mustang.
Unfortunately, the evidence appears to be in strong support of your neighbor’s
claim. Your only chance to defend yourself is to present an argument that
the ball possessed less kinetic energy when it fell than when it was served so that,
even according to the neighbor’s own data, the ball could not have damaged
the car.
SAFETY
• Perform this experiment in a clear area.When tossing balls for the
experiment, throw the balls straight up and catch them as they
approach the ground. Do not throw balls around the room.
• Tie back long hair, secure loose clothing, and remove loose jewelry to
keep them from getting in the way.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
36 HOLT PHYSICS Technology-Based Lab Activities