Momentum u0026 Conservation of Energy Quiz Quiz

Explore key concepts of momentum and the conservation of energy with this engaging quiz. Challenge your understanding of collisions, energy transformations, and the principles behind these foundational physics topics.

1. Momentum of Moving Objects

   A 2 kg object travels at 5 meters per second in a straight line; which option represents its momentum in standard SI units?

   1. 2 newtons
   2. 7 joules
   3. 0.4 watt
   4. 10 kilograms-meter per second

   Explanation: Momentum is calculated as mass times velocity, so 2 kg times 5 m/s equals 10 kilograms-meter per second. Joules are units of energy, not momentum. Watts measure power, and newtons measure force, making them incorrect in this context.

2. Types of Collisions

   In a perfectly elastic collision between two objects, which physical quantity is conserved besides momentum?

   1. Potential energy
   2. Kinetic energy
   3. Thermal energy
   4. Angular momentum

   Explanation: In perfectly elastic collisions, both momentum and kinetic energy are conserved. Thermal energy is not conserved because it can be generated due to friction. Potential energy is only relevant if there are changes in height or compression and does not directly apply here. Angular momentum is conserved in rotational systems, but not necessarily in linear collisions.

3. Conservation of Energy Example

   A ball is dropped from a height and bounces back to half its original height; which statement best explains what happens to its initial potential energy?

   1. The energy is completely destroyed
   2. All the energy is stored as elastic potential energy
   3. Some energy is transformed into other forms, such as heat or sound
   4. There is no loss of energy during the bounce

   Explanation: When the ball bounces and does not return to its original height, some of its initial potential energy is lost to heat, sound, and deformation. Not all energy is stored as elastic potential energy; otherwise, the ball would bounce back to its original height. No energy is completely destroyed, only transformed. The third option is incorrect since there is clearly a reduction in bounce height.

4. Impulse and Force Relationship

   If a hockey puck experiences a force of 3 newtons for 2 seconds, what is the change in its momentum, also known as impulse?

   1. 0.67 meters per second
   2. 1.5 joules
   3. 6 newton-seconds
   4. 5 watt-seconds

   Explanation: Impulse is calculated as force times the duration of the force, so 3 newtons times 2 seconds equals 6 newton-seconds. Joules are a unit of energy, not impulse. Watt-seconds is a unit of energy as well and does not apply here. 0.67 meters per second could be a change in velocity, but not in this context.

5. Closed Systems and Conservation Laws

   Why is it necessary for a system to be closed and isolated for momentum to be conserved during an event?

   1. Collisions must be inelastic
   2. Only potential energy should be present
   3. Energy inside the system must increase
   4. No external forces should act on the system

   Explanation: For momentum to be conserved, the system must not experience any net external force; otherwise, momentum can change. An increase in energy is not a requirement for momentum conservation. Potential energy is not the only form of energy in such events. Collisions can be either elastic or inelastic as long as the system is closed and isolated.