Work & Energy

A box of mass m is pulled by a force F, which makes

an angle 𝜙 with the horizontal. A frictional force f is

applied on the box as it slides on a horizontal surface,

as shown in the figure below. Which of the following

represents the net work on the box when it covers a

distance d?

• 𝐹𝑑

• (𝐹 − 𝑓)𝑑

• 𝐹 cos 𝜙 𝑑

• (𝐹 cos 𝜙 − 𝑓)𝑑

• (𝐹 sin𝜙 − 𝑓)𝑑

A boy pushes a 35 kg crate across a horizontal floor

with a force of 250 N. The coefficient of kinetic

friction between the crate and the floor is 0.30. How

far does the crate move if the net work on it is

2400 J?

• 8.5 m

• 12 m

• 16 m

• 21 m

• 26 m

The net force on an object is represented in the

force-position graph shown below. Find the work

done on the object as it moves from x = –20 m to x =

40 m.

• 20 J

• 30 J

• 40 J

• 60 J

• 90 J

A 10 𝑘𝑔 block is released from rest at the top of an

inclined plane of height h = 2m, as shown in the

figure below. The coefficient of kinetic friction

between the block and the surface of the incline is

0.2.

What's the work done by the normal force?

• -350 J

• -200 J

• 0 J

• 200 J

• 350 J

The velocity of a 2.00 kg object, which starts

moving from rest, is given by the equation:

𝑣 = 4.00𝑡² + 7.00𝑡

Find the net work done on the object between

t = 0.00 s and t = 3.00 s.

• 5.70 × 10¹ 𝐽

• 1.14 × 10² J

• 1.09 × 10³ J

• 3.25 ×10³ J

• 6.50 × 10³ J

A particle moving on the x-axis has a potential energy

given by the equation below.

𝑈 = 8𝑥² − 4𝑥 + 400.

The force on the object at x = 1.00 m is _______.

• 0.00 N

• 12.0 N in the (+) x-axis

• 12.0 N in the (–) x-axis

• 20.0 N in the (+) x-axis

• 20.0 N in the (–) x-axis

A particle moving on the x-axis has a potential energy

given by the equation below.

𝑈 = 8𝑥² − 4𝑥 + 400.

Its state of equilibrium will be at ____.

• 𝑥 = 0.025 𝑚

• 𝑥 = 0.25 𝑚

• 𝑥 = 2.5 𝑚

• 𝑥 = 25 𝑚

• 𝑥 = 250 𝑚

The net force acting on a particle moving on the xaxis

is given by:

𝐹 = −9𝑥² + 4𝑥 + 2

Find the change in the potential energy of the particle

as it moves from x = 0.00 m to x = 2.00 m.

• -36.00 J

• -12.00 J

• 0.00 J

• 12.00 J

• 36.00 J

A certain one-dimensional conservative force is

given as a function of 𝑥 by the expression 𝐹 = −𝑘𝑥³,

where 𝐹 is in newtons and 𝑥 is in meters. A possible

potential energy function 𝑈 for this force is ____.

• 𝑈 = −1/2 𝑘𝑥⁴

• 𝑈 = 1/2 𝑘𝑥⁴

• 𝑈 = −1/4 𝑘𝑥⁴

• 𝑈 = 1/4 𝑘𝑥⁴

• 𝑈 = −3 𝑘𝑥⁴

A block slides from rest with negligible friction

down the track below, descending a vertical height of

5.0 m to point 𝑃 at the bottom. It then slides on the

horizontal surface. The coefficient of friction between

the block and the horizontal surface is 0.20. How far

does the block slide on the horizontal surface before

it comes to rest?

• 0.4 m

• 1.0 m

• 2.5 m

• 10 m

• 25 m