Work and Power Practice

Multiple Choice

The SI Unit for Work

• Newton (N)

• Joule (J)

• Second (s)

• Watt (W)

Multiple Choice

The SI Unit for Power

• Newton (N)

• Joule (J)

• Second (s)

• Watt (W)

Multiple Choice

A mountain climber with a force of 90 N scales a 100 m cliff. How much work is done by the mountain climber?

• 1.11 W

• 90,000 J

• 0.9 J

• 9 W

Multiple Choice

How far does a car that weighs 5,000 N go if 18,000 J of work is done on it?

• 3.8 m

• 3.7 m

• 3.2 m

• 3.6 m

Multiple Choice

You do 90 joules of work in 30 seconds. How much power have you generated?

• 30 watts

• 3 watts

• 120 watts

• 270 watts

How POWERFULis she?

When doing a chin-up, Elise lifts her 425 N body
up a distance of 0.25 meters in 2 seconds. What

is the power delivered by her biceps?

W = ?
F = 425 N
d = .25 m
t = 2 s
P = ?

W = Fd

W = (425N)(.25 m)

W = 106.25 Nm

or 106.25 J

P = W/t

P = 106.25 J/ 2 s

P = 53.125 J/s

or 53.125 Watts (W)

Weight vs Mass Video

Weight = Newtons (N)

The amount of force
acting on a mass due to
the acceleration of
gravity. It changes
depending where you
are in the Universe.

Mass = Kilograms (Kg)

The amount of matter in
an object. Stays the
same no matter where
you are.

What is the work done by Tyse who lifts a 30 kg TV

straight up 1.5 meters?

If it takes 0.5 secs, what is his power rating?

W = ?
m = 30 kg
d = 1.5 m
t = 0.5 s
P = ?

W = Fd

Fw = mg

Fw = (30kg)(9.8 m/s2)

Fw = 294 N

W = (294 N)(1.5 m)

W = 441 Nm

or 441 J

P = W/t

P = 441 J / 0.5 s

P = 882 J/s

or 882 W

How much time did it take for Vrishank to lift a 10 kg
dog crate 4 meters if his power rating was 160 Watts?

t = ?
m = 10 kg
d = 4 m
P = 160 W
W = ?

W = Fd

Fw = (10kg)(9.8 m/s2) = 98 N

W = Fd = (98N)(4m) = 392 J

P = W/t ….. So t = W / P

t = (392 J) / (160 W) = 2.45 seconds

Practice identifying the units in the Work and Powerformulas.

Fill in the blanks with the units for the formulas in #1 and #2.

1. Work (___) = Force (____) x Distance (___)


2. Power (___) = Work (___) / time (____)

Joule

Newton

Meter

Watt

Joule

second

REFLECTION: In your own words, describe the
relationship between Work and Power. How will

you keep them straight without confusion?

Multiple Choice

If 150 Joules of work is needed to move a box 10 meters, what force was used? 

• 1500 N

• 15 N

• 1.5 N

• 150 N

Multiple Choice

How much work is done in holding a 15 N sack of potatoes while waiting in line at the grocery store for 3 minutes?

• 15 J

• 45 J

• 0 J

• 5 J

Drag and Drop

If a mass in lifted the same vertical distance (same work done) but the time is increased, the power

Placeholder

Drag these tiles and drop them in the correct blank above

Decreases

Increases

Remains the same

Multiple Choice

A 5 kg rock is lifted 2 m. Find the amount of work done.

• 10 J

• 980 J

• 9.8 J

• 98 J

POWER LAB

Work

The work done is:
W = Fd
= force x distance

= weight x height
= (mg)(h)

W = Potential Energy
Work = mgh

Weight

Normal Force

Where to?

1st floor

2nd floor

3rd floor

4th floor

Group 1

Group 2

Group 3

Group 4

Group 5

Group 6

Group 7