Work and Energy

The principle of work and energy is used for solving problems that involve. Select all that apply.

• Velocity

• Acceleration

• Force

• Distance

• Displacement

A work of the force is ____________ if the force and displacement are in the same direction.

• positive

• negative

• it depends on the problem

The work of weight is _____________ if the particle is moving up an incline.

• positive

• negative

• it depends on the problem

Write the equation for kinetic energy.

The definition for power is:

• dU/dt

• $F\cdot v$

• $F\cdot\frac{dr}{dt}$

• All of the above

The unit of power in the SI system is:

• hp

• Joule

• Newton

• Watt

If a 100 N force is pulling the 100 kg crate up the smooth incline shown, what is the total work of all forces acting when the crate moves a distance of 2 m?

In the problem above, what is the Power done by the force, F (100 N moving a distance of 2m), at t = 3 sec, if the crate starts from rest and moves with an acceleration of 2 m/s²?

If the spring starts in the unstretched position and then a force of 50 lb compresses it by 2 inches, what is the work done by the spring? Spring constant is 10 lb/ft.

How well do you understand Work and Energy so far?

• Very well!

• Pretty well, still need practice

• Not well at all; totally confused!