Lab 8: Mechanical Energy PDF

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Amelia Lobo PHYS 123 A20437425 Lab 8: Mechanical Energy (a) For the first experiment, explain why work done by the falling mass is independent of the path taken. The work done is a conservative force therefore it is independent of the path taken. The height at where the falling mass starts has an initial gravitational potential energy. How the object got to the initial height is irrelevant because it has the same gravitational potential energy and falls straight down.

(b) What did the addition of a spring do to the overall system? Is this spring force a conservative force? The cart on the track goes slower with the addition of the spring because potential energy from the falling mass is converted into elastic potential energy of the spring. The spring force is a conservative force because it is independent of the path taken and only relies on the initial and final positions.

(c) Write down the energy equation relations for the second experiment.

1 2 m 2 g y i= k x +m 2 g y f , where m2 is the mass on the air track, yi is the initial height of the falling 2 mass, yf is the final height of the falling mass, k is the spring constant and x is the horizontal displacement.

(d) Where does the maximum kinetic energy in parts 1 and 2 occur? The maximum kinetic energy in part one occurs when the falling mass is about to stop at its final position. It occurs in part two just before the mass on the track stops

(e) Can we truly ignore friction in this lab? Explain using your data. Spring potential energy Potential Energy

0.01470511

0.0330865

0.0588204 4

0.063765

0.0956475

0.12753

The spring potential energy and the potential energy of the falling mass should be equal because potential energy from the falling mass is converted into elastic potential energy of the spring. However, a lot of the energy is lost because the spring potential energy is always less then the falling mass potential energy. Therefore, friction cannot be truly ignored because the energy “lost” is the force of friction on the system.

Amelia Lobo PHYS 123 A20437425 (f) Calculate the ratio of the kinetic and potential energies for parts 1 and 2. What do these ratios tell you about the conservation of energy? Part 1: Kinetic Energy

Potential Energy

Ratio

0.06739948

0.073575

0.91606495

0.08996121

0.0981

0.91703579

0.1120791

0.122625

0.91399878

Kinetic Energy

Potential Energy

Ratio

0.02643907

0.01470511

1.79795124

0.02553959

0.0330865

0.77190368

0.01442918

0.05882044

0.24530894

Part 2:

The ratios in part 1 are very close to 1.0. This shows that most of the conservation was conserved. The potential and kinetic energies should be equal in order to conserve the energy therefore the ratios should be close to 1. In the second part of the experiment the ratios vary greatly and are not generally close to 1. This means that the energy was not conserved and much of the energy was “lost” by another force acting upon the system. (g) What effect would the release point have on the final velocity? The final velocity of the cart on the track will be much higher if the falling mass is released from a higher point....