Lesson 8
Work
• Work – when a force acts on an object and
it moves some distance.
WORK = Force (N) x Distance (m)
L8
WORK
Alice pulls a sled with a force of
12 N. She pulls the sled
through a distance of 5 m.
How much work does Alice do
on the sled?
L8
WORK
Work = force x distance
Work = 12 N x 5 m = 60 N-m
L8
WORK
Michael lifts his book bag, which
weighs 25 N, from the floor to a
desktop that is 0.80 m above the
floor. How much work does
Michael do on the bag?
L8
WORK
Force x Distance = WORK
25 N x 0.80 m = 20.0 N-m
L8
Inquiry 8.1
Calculating the Work Done
on Different Surfaces
SURFACE
TABLETOP
WAXED
PAPER
PAPER
TOWEL
FINE
SANDPAPER
COARSE
SANDPAPER
L8
EFFORT
FORCE (N)
EFFORT
DISTANCE (m)
WORK DONE
(N-m)
• 1. What force are you
working against when you
lift a backpack?
•
L 8.1b
• 2. In which of the following cases
is work, as defined by scientists,
being done?
• A. Someone tries to move a
piano, but the piano won’t budge.
•
L 8.1b
• B. A tow truck is pulling a
car slowly along the street.
•
L8.1b
• C. A student is studying for
a mathematics exam.
L 8-1b
• D. A student is pushing
a grocery cart around a
store.
•
L 8.1b
• E. Another student is
standing in line holding a
12-N bag of potatoes.
•
L 8.1b
• F. A student pushes
against the school building.
•
L 8.1b
Lesson 8
Question – Lesson 8
• Is the motor capable of doing enough work
to lift the sled to a distance of .10 m?
• Lesson 8
• If _________________,then __________
because _________________.
• Lesson 8
•
•
•
•
Materials
1.
2.
3.
• Lesson 8
Lifting a Load
• 1. Motor force with three batteries in
series: _________________
• 2. Work done by a motor when it lifts a
load 10.0 cm. (0.10 m)
• Work = _______ x _______ = ______
L 8-2
3. Weight of six washers:______________
4. Work to raise six washers:
Work = ______ x _______ = _______
5. Your estimate of sled’s weight: _______
6. Sled’s actual weight: _________
L 8-2
7. Work to lift sled 10.0 cm. (0.10 m):
Work = _________ x ______ = _______
L 8-2
• Lesson 8
Vocabulary – Lesson 8
•
What happens when an object changes its position by moving in
the direction of the force that is being applied is
(62) work.
• Work = force x distance (w = fd)
• Work involves a force applied across a distance.
•
The metric unit of work is the
(63) newton-meter (N-m).
•
A newton-meter is also a
(64) joule (J).
•
James Joule – described the relationship between work and energy.
L8
Vocabulary – Lesson 8
• A force is applied to lift the sled. This is
the
(65) effort force.
• The distance the sled moves is the
(66) effort distance.
Vocabulary – Lesson 8
• Electric current flows through the wire. The unit
used to describe how much electric current flows
through a wire is the
(67) ampere (amp).
• Andre Ampere
• The electric potential of a battery is measured in
(68) volts.
• Alessandra Volta