Structure Questions – Understanding Energy

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Diagram 5.1 (a) shows a boy skating down a ramp from position \(X\). Diagram 5.1 \((b)\) shows the velocity-time graph of the boy from \(X\) to \(Z\).
Diagram \(5.2(a)\) shows the same boy skating down from position \(Y\) by using another ramp. Diagram \(5.2(b)\) shows the velocity-time graph of the boy from \(Y\) to \(Z\).

Both ramps are of the same slope and surface.

  1. Name the physical quantity represented by the gradient of the velocity-time graph. [1 mark]
    Acceleration 
  2. Observe Diagram 5.1 (a) and Diagram \(5.2(a)\).
    1. Compare the gravitational potential energy of the boy at \(X\) and \(Y\). [1 mark]
      The gravitational potential energy in Diagram \(5.1\) is higher than that of in Diagram 5.2.
    2. Compare the velocity of the boy at \(Z\) in these two situations. [1 mark]
      The velocity of the boy at \(Z\) in Diagram \(5.1\) is higher than his velocity in Diagram 5.2.
    3. Compare the kinetic energy of the boy at \(Z\) in these two situations. [1 mark]
      The kinetic energy of the boy at \(Z\) is higher than his kinetic energy in Diagram \(5.2\).
  1. Based on the answer in \(5 (b)\),
    1. state the relationship between the gravitational potential energy and kinetic energy of the boy. [1 mark]
      When gravitational potential energy increases, the kinetic energy increases.
    2. state the physic concept involved. [1 mark]
      Principle of conseryationi of energy
  2. Based on Diagram \(5.1(a)\),
    1. what happens to the velocity of the boy when he skates from \(Z\) to \(Q\) ? [1 mark]
      Decreases
    2. Give one reason for the answer in \(5 (d)( i )\). [1 mark] 
      The kinetic energy of the boy changes to potential energy.