Physics: Conservation of Energy Lab Answers

Problem:

How can an experiment be designed to measure the change in gravitational potential energy and the change in kinetic energy as an object rolls down a ramp?

Predictions:

Chemical energy is used by the body to lift the car 10 centimeters up onto the top of the ramp. When the energy is not being used it is stored in the liver or as fat on the body. When it is not used by the human for lifting carts, it can be used for other things such as breathing and digesting. While the cart is being lifted other energy that is useless, such as body heat, is also created.

While the object rolls down the ramp the potential gravitational energy is being transferred into kinetic energy because of the movement of the cart. Since energy cannot be destroyed, at the bottom of the ramp when the car is stopped, the energy has been transferred to the surface the object is rolling on.

Equipment:

• iBook computer
• motion sensor and USB connector
• cart
• balance
• ramp

Procedure:

Refer to pages 47 and 48 in York Mills Collegiate yellow physics book.

Analyze and Conclude:

Mass of cart = 275 grams

Sin x = 100/10

Sin x = .1

Angle of incline = 5.74 degrees

Velocity-Time Graph

Kinetic Energy (1/2*275*v^2)-Time Graph

Potential Energy (275*9.8*(d*.1))-Time Graph

When we compared the potential energy-time graph and the kinetic energy-time graph we noticed that the potential energy decreased while the kinetic energy increased. As the car does down the ramp it loses height, thus losing potential gravitational energy and gaining kinetic energy as it is moving with more speed.

Mechanical Energy ((1/2*275*v^2)+(275*9.8*d*.1)–Time Graph

The mechanical energy-time graph shows an almost straight line which proves that the force of gravity is conservative. Some energy is missing near the end of the run and this energy might have left the experiment because of the force of friction. Friction was not taken into consideration in this experiment and could have very easily resulted in a loss of energy.

Conclusion:

After this experiment was done the mechanical energy-time graph showed a fairly straight line. It showed this line because gravity, a conservative force, was used to move the cart. Since the force was conservative, the mechanical energy throughout the experiment stayed the same, with no energy being lost or gained.

The gravitational potential energy is being transferred to kinetic energy since the object is not at a rest and is moving down the ramp, as shown in the kinetic energy-time graph and potential energy-time graph. Since the energy remains constant throughout the whole run, gravity is a force that is conservative.