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Attempts 127

If you double the speed of a moving object, what else doubles?

  1. A
    Its potential energy
  2. B
    Its kinetic energy
  3. C
    Its acceleration
  4. D
    Its momentum

Topic Flashcards

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Question

What is the definition of linear momentum (p), and how is it mathematically related to mass (m) and velocity (v)?

Answer

Momentum (p) is the product of an object's mass and its velocity: p = m * v. It is a vector quantity with direction the same as the velocity.

Question

If speed doubles, what happens to kinetic energy? Write the kinetic energy formula and show the calculation for a change from v to 2v.

Answer

Kinetic energy quadruples. KE = ½ * m * v². For speed 2v, KE_new = ½ * m * (2v)² = ½ * m * 4v² = 4 * (½ * m * v²) = 4 * KE_original.

Question

A 5 kg object moves at 4 m/s. Calculate its momentum and kinetic energy. What are the new values if its speed doubles to 8 m/s?

Answer

Original: p = 5 kg * 4 m/s = 20 kg·m/s; KE = ½ * 5 * (4)² = 40 J. Doubled speed: p = 5 kg * 8 m/s = 40 kg·m/s (doubled); KE = ½ * 5 * (8)² = 160 J (quadrupled).

Question

Why does potential energy not double when speed doubles? On what does gravitational potential energy (a common type) depend?

Answer

Gravitational potential energy (PE = m * g * h) depends on height (h), not speed. Changing an object's speed at the same height does not change its potential energy.

Question

In a car crash, why is the damage much more severe at 60 mph compared to 30 mph, given that the momentum only doubles?

Answer

While momentum doubles, the kinetic energy quadruples. The work needed to stop the car (and the damage done) relates to the energy dissipated. Quadruple the energy means a far more severe collision.

Mini Quiz

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If you double an object's speed, does its kinetic energy also double?

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