Download Chapter 3 Review Questions

Laws of Motion Review Questions
Name _________________________
Round all calculations. Given, formula, setup & solution is required.
1. State Newton’s 1st Law of Motion – An object maintains a constant velocity unless a net force acts on it
2. The tendency of an object to resist any change in motion is called Inertia.
3. What is required to accelerate an object? Net Force
4. Write the equation that represents Newton’s 2nd Law of Motion F = ma or a = F/m or m = F/a
5. T/F If equal forces are applied to two objects, the object with greater mass will accelerate faster than the
object with less mass.
6. How much force is required to accelerate a bowling ball with a mass of a 7 kg at 11m/s2?
F = m∙a
m = 7 kg
a = 11 m/s/s
F = 7kg ∙ 11 m/s/s
F = 77 N
7. Calculate the mass of a bowling ball that weighs 75 N.
Wt (or F) = 75 N
g (or a) = 9.8 m/s/s
m = F/a
m = 75 N / 9.8 m/s/s m = 7.65 kg
Your little brother (if you don’t have one just play along) asks you to pass the milk at dinner. You decide to
slide it across the table. The milk jug has a mass of 2 kg and you apply a force of 4 N.
8. What is the rate of acceleration for the milk jug?
m = 2 kg
F=4N
a = F/m
a = 4 N / 2 kg
a = 2 m/s/s
9. If it takes you .85 seconds to accelerate the jug, how fast is it going when it leaves your hand? (Hint: use
your answer from the previous question in your calculation)
a = 2 m/s/s
t = .85 s
v = a∙t
v = 2 m/s/s ∙ .85s
v = 1.7 m/s
10. State Newton’s 3rd Law of Motion – For every action there is an equal and opposite reaction
11. According to Newton’s third law of motion, if you apply a force of 3 N to a wall, the wall must apply a
force of 3 N on you.
12. State the Law of Conservation of Momentum – in a collision total momentum is conserved or Total
momentum before a collision = total momentum after a collision
13. What is the momentum formula? P = m∙v or m = P/v or v = P/m
14. Which would have more momentum moving at the same speed down the grocery aisle, a full shopping cart
or an empty shopping cart? Explain your answer.
Full cart – since v is the same the mass makes the difference and the full cart has more mass so more P
15. What is measured in m/s2? acceleration
18. What is the metric standard unit for force? N
16. What is measured in m/s? velocity
19. What is the metric standard unit for weight? N
17. What is the metric standard unit for mass? kg
20. What is the metric standard unit for inertia? kg
Laws of Motion Review Questions
Name _________________________
A grocery cart with a mass of 50 kg is moving at a velocity of 4.0 m/s West. It bumps into another cart with a
mass of 40 kg moving in the same direction at 2.0 m/s. The two get locked and move off together. Assume that
the Law of Conservation of Momentum is in effect.
21. Calculate the momentum of each cart separately before they collide.
m1 = 50 kg
P1 = m1∙v1
v1 = 4 m/s W
P1 = 50 kg∙4 m/s W
m2 = 40 kg
v2 = 2 m/s W
P1 = 200 kg∙m/s
P2 = m2∙v2
P2 = 40 kg ∙ 2 m/s W
P2 = 80 kg∙m/s
22. Calculate the total momentum and the total mass of the two carts right after the crash?
PT = P1 + P2 = 200 kg∙m/s + 80 kg∙m/s = 280 kg∙m/s
mT = m1 + m2 = 50 kg + 40 kg = 90 kg
23. Moments after the crash, what is the velocity of the two carts together?
mT = 90 kg
v = P/m
v = 280 kg∙m/s / 90 kg
PT = 280 kg∙m/s
v = 3.1 m/s
24. Draw and Label at least 2 (total of 4 arrows) action-reaction pair forces involving the
fish on the diagram to the right.
1
1 = Force of hook on fish
2
2 = Force of fish on hook
3 = Force of fish on Earth
These 2 (3 & 4) make up the force of gravity
4 = Force of Earth on fish
25. Calculate the Net force on the person from the diagram below.
Eliminate the forces not on the person & you end up with 1000 N up & 900 N down
Since they are opposite you subtract so
NF =1000 N up – 900 N down
NF = 100 N up
3
Force of board on person (1000 N)
Force of person on earth (900 N)
4
Force of person on board (1000 N)
Force of earth on person (900 N)
26. Calculate the mass, net force and acceleration of a 1000 N skydiver experiencing 250 N of air resistance
AND draw & label the unbalanced forces on the skydiver.
mass = 102 kg
Net Force = 750 N down
Acceleration = 7.35 m/s/s
Mass: Wt = 1000 N, g = 9.8 m/s/s; m = Wt/g (F/a); m = 1000N/9.8 m/s/s; m = 102 kg
Net Force: (opposites subtract) 1000 N down – 250 N up = 750 N down
Acceleration: m = 102 kg, F = 750 N; a = F/m; a = 750 N/102 kg; a = 7.35 m/s/s