VOCABULARY:
Work
Joule
Lever
Fulcrum
Pulley
Wheel and axle
Inclined plane
Wedge
Screw
Machine
Compound machine
Net force
Unbalanced forces
Balanced forces
Mass
Friction
Gravity
Weight
1. In order for work to be done, what 2 things MUST happen? Force must act in the same direction of
motion
2. If the object doesn’t move has work been done on the object? no
3. Give an example of doing work on an object.
4. Is carrying a bag of groceries work? Why or why not? No because the force is acting up and the
motion is in a different direction
5. Draw the work triangle.
6. What is the unit for work? Joules or Newton meter (Nm)
7. What two things affect friction? Types of surfaces and how hard they are pushed together
8. What are the 4 types of friction and an example of each? Rolling: ball, sliding: pushing a box, fluid:
bird flying and engine and oil, static: desk sitting still, parked car
9. Draw a picture of a wheel and axle. Give an example of a real life wheel and axle. car wheels, faucet,
screwdriver
10. Draw a picture of an inclined plane. Give a real life example of the use of an incline plane. ramp
11. What is the function of a screw? Draw a picture of one Increases distance to make force less, it is
an inclined plane wrapped around a cylinder.
12. What is function of a wedge? Draw a picture of one. Cut apart, zipper, axe, teeth
13. How does a pulley make work easier? Draw an example of a pulley showing the direction of the
forces. Change the distance, to make force easier
Calculate the net force on the object described in each situation. Draw a free diagram for each and
show the directions of forces as well as the total net force and direction of net force.
Example: Mr. Burke lifts the heavy box over his head with one push of the arm and a force of 250 newtons.
Gravity is pulling down the mass with 200 Newtons. What is the net force and direction of the box?
Force of Mr. Burke’s arm (250 N)
Net force =
50 N
upwards
Force of gravity
(200N)
1. A box is being pushed by two stellar science students, one on each side of the box. Dalton is pushing
the box with a force of 10 N to the left. Andy is pushing the box with a force of 15 N to the right. Who is
the stronger individual and what is the net force and direction on the box? Andy 5N to the right
2. During tug of war Janelle felt she was supergirl and attempted to beat Ronnie. Janelle with one arm on
the rope and the other at her side applied a 100 N force to the left, while Ronnie applied a 100 N force
with both hands to the right. What is the net force and direction on the rope?
0 net force
3. Janelle finally decided to take this seriously and put both hands on the rope and applied a 150 N force
to the left, while Ronnie still struggled with his 100 N force to the right. What is the net force and
direction of motion?
50 N to the left, Janelle was the winner!
4. Sarah and Kevin were attempting to push Jack on the scooter with enough force so Jack would run into
Mr. Burke. They figured out they needed a 50 N force to run the scooter into Mr. Burke. Sarah and
Kevin were both applying force toward Mr. Burke. Sarah was applying a 20 N force to the left, and
Kevin was applying (with all of his strength) a force of 15 N to the left. Did the scooter rocket that Jack
was riding on hit Mr. Burke. Explain how they can get it to hit him.
No, 15 Newtons
5. In a third period battle the girls were able to overcome the boys 3 times in the tug of war. The boys had
8 individuals each pulling with a force of 30 N. The 10 girls were able to pull the rope toward them with
a net force of 50 N. What was the minimum amount of force each of the 10 girls applied to the rope?
6. During 4th period Josh was a beast. He resisted the forces applied by 5 people in his class all at once.
Each person applied a force of 17 N and Josh still did not move. How much force was Josh pushing
back with and how many people would it take to push Josh if he can withstand a force of 250 N?
7. During 4th period we put Claudia in a box because she was talking too much. We still heard her voice
through the box so we decided to push her outside. The force of friction of the ground on the box was
68 N. If Mr.Burke can apply a force of 25 N and every other 7th grade student can apply a force of 6 N.
How many students would Mr. Burke need to make the box start moving and go outside? (Think
quickly, the faster we move the box out, the quicker she stops talking)