Physics Work, Power & Energy Review - Concepts

If an object experiences an impulse and stops, what is its final momentum?

• Zero

• Equal to the impulse

• Equal to the initial momentum

• Cannot be determined

Answer explanation

When an object experiences an impulse and stops, its final momentum is zero. This is because momentum is conserved, and if the object comes to a complete stop, it has no momentum left.

Potential energy is defined as the energy possessed by an object due to its position or state. Which of the following best describes potential energy?

• Energy due to motion

• Energy due to position or state

• Energy due to temperature

• Energy due to chemical reaction

Answer explanation

Potential energy is specifically defined as the energy an object has due to its position or state, making 'Energy due to position or state' the correct choice. The other options refer to different forms of energy.

If the force applied to an object remains constant, is more power needed for the object to move faster?

• Yes, more power is needed for the object to move faster.

• No, the power remains the same regardless of speed.

• Power is not related to speed in this context.

• It depends on other factors.

Answer explanation

Yes, more power is needed for the object to move faster because power is the rate at which work is done. If the force is constant, increasing speed requires more work done in the same time, thus increasing power.

Which of Newton’s laws explains how momentum is conserved in all interactions between objects?

• Newton's First Law

• Newton's Second Law

• Newton's Third Law

• Law of Universal Gravitation

Answer explanation

Newton's Third Law states that for every action, there is an equal and opposite reaction. This principle explains how momentum is conserved in interactions, as the forces between objects are equal and opposite, maintaining total momentum.

Work is measured in what unit? What base units make up this unit?

• Joule; Newton meter

• Watt; Joule per second

• Pascal; Newton per square meter

• Newton; Kilogram meter per second squared

Answer explanation

Work is measured in Joules, which is defined as a Newton meter. This means that one Joule is the work done when a force of one Newton is applied over a distance of one meter.

What is the equation for gravitational potential energy?

• GPE = mgh

• GPE = Fd

• GPE = ma

Answer explanation

The equation for gravitational potential energy (GPE) is GPE = mgh, where m is mass, g is the acceleration due to gravity, and h is the height above a reference point. This formula calculates the energy stored due to an object's position in a gravitational field.

The law of conservation of energy states that energy cannot be:

• created or destroyed, only transformed from one form to another

• created but can be destroyed

• destroyed but can be created

• created and destroyed

Answer explanation

The law of conservation of energy states that energy cannot be created or destroyed, only transformed from one form to another. This means energy is always conserved in a closed system.

Can an object have both kinetic energy and gravitational potential energy?

• Yes, an object can have both kinetic energy and gravitational potential energy simultaneously.

• No, an object cannot have both kinetic energy and gravitational potential energy simultaneously.

• An object can only have kinetic energy, not gravitational potential energy.

• An object can only have gravitational potential energy, not kinetic energy.

Answer explanation

Yes, an object can have both kinetic energy and gravitational potential energy simultaneously. For example, a ball thrown upwards has kinetic energy due to its motion and gravitational potential energy due to its height.

What is the rest position of a spring called?

• Equilibrium position

• Neutral position

• Resting point

• Static point

Answer explanation

The rest position of a spring is called the equilibrium position. This is where the spring is neither compressed nor stretched, resulting in a net force of zero.

If a spring is stretched to twice the length of its equilibrium position, by what factor does the energy stored in the spring change?

• 1

• 2

• 3

• 4

Answer explanation

The energy stored in a spring is given by the formula E = 1/2 k x^2, where x is the displacement. If the spring is stretched to twice its length (x = 2x0), the energy becomes E = 1/2 k (2x0)^2 = 4(1/2 k x0^2), thus increasing by a factor of 4.