force and motion test review

Force and Motion Test Review

1. What is a force? A Push or a Pull

2. What is the difference between balanced forces and unbalanced forces?

Balanced forces - cancel each other out, so there is no change in motion/acceleration. Net force =0. Unbalanced forces – one force is greater than another, so there is a change in motion. Net force > 0

3. Draw a situation where the forces are balanced. Make sure your diagram is labeled.

No change in motion (no change in acceleration)

4. Draw a situation where the forces are unbalanced. Make sure your diagram is labeled.

Team 1- 100N Team 2 – 75N

Motion to the left

5. What is net force? The total of the forces acting on an object

6. If my dog, Bella, is pulling a rope with a force of 80N to the left and my friend’s dog, Lucy, is pulling on the opposite end with a force of 30N to the right, what is the net force of the rope? What direction is the rope being pulled in? The net force is 50 N to the left

80N

30N

7. Match the left column to the correct answer in the right column. Describe the forces in each box on the left, and explain the resultant forces on the right.

8. Three forces act on a box that is initially at rest as shown below. Determine the net force acting on the crate and describe the resulting motion of the crate.

0 Newtons – Object remains motionless (no acceleration)

9. Five different forces act on an object. Is it possible for the net force on the object to be zero? Explain.

Yes – they could result in a net force of 0 N. See image.

40 N

40 N

10 N

20 N

50 N

10. What three things can happen to an object when an unbalanced force acts on it?

(Change in acceleration) - An object can start moving, stop moving, or change direction

11. What is Inertia? Give an example.

The tendency of an object to resist a change in motion or its position. EX: If you are not wearing a seatbelt when a car suddenly stops, you will continue to go forward, even after the car stops.

12. Compare inertia of an object with a smaller mass to the inertia of an object with a larger mass. The greater the mass, the greater the inertia.

13. Newton’s LawsNewton’s Law of Motion Description Formula or Example

First Law of MotionLaw of Inertia

An object at rest will stay at rest, an object in motion will stay in motion unless acted on by an unbalanced force.

When a car stops the passenger continues to go forward

Second Law of Motion

Law of Force and Acceleration

The net force on an object will cause it to accelerate inversely proportional to its mass

Formula: Force = Mass x Acceleration Things to keep in mind: Acceleration decreases as mass increases

Third Law of Motion

Law of Action - Reaction

If one object exerts a force on another object, then the second object exerts a force of equal strength in the opposite direction on the first object.

Squid swimming or bungee jumping

14. Explain the following scenarios in terms of Newton’s Laws of Motion:

a.Julian was riding his bike and ran into a parked car. He was thrown off the bike when he hit the parked car. Law of Inertia – Julian was moving forward, so even though his bike stopped moving he continued to move forward.

b.Arthur plays baseball and throws a pitch to the batter. The batter hits the ball back to the pitcher’s mound. Law of Action-Reaction – The ball exerted a force on the bat and the bat exerted an equal and opposite force on the ball.

c.An iguana has more trouble pushing a boulder than a pebble. Law of Force and Acceleration – The iguana would have to apply more force to the boulder to maintain the same acceleration.

d.You jump higher when you give more thrust to your legs. Law of Force and Acceleration – you apply a greater force to achieve a greater acceleration.

e.A student dove off the back of a motionless boat and the boat moved forward. Law of Action-Reaction – The diver applies a force to the boat and the boat applies an equal and opposite reaction to the diver

f. When you jump off of a moving swing, it keeps on going. Law of Inertia – the swing continues to move because it was already in motion. It will continue to move until an unbalanced force acts upon it.

15. What are two ways you can increase the acceleration of an object?

Decreasing massIncreasing force

16. What is gravity? The force that pulls objects toward each other.

17. How does friction affect an object’s motion? Friction causes objects to slow down and eventually come to a stop

18. Which forces would eventually cause a rolling ball to come to a stop?

Friction and gravity

19. A 250 kg trailer is being pulled by a truck. The force causes the trailer to accelerate at 4 m/s2. What is the net force that causes this acceleration? Show your work-don’t forget units!

Force = mass X AccelerationForce = 250kg X 4 m/s2

Force = 1000 N

20. Hannah uses a force of 60 N to move a 30 kg bag of equipment. What is the acceleration of the bag? Show your work-don’t forget units!

Force = mass X Acceleration60 N = 30 kg X Acceleration60/30 = 30 X Acceleration/302 m/s2 = Acceleration

21. Johnny’s balloon car travels a distance of 200 cm in 50 s. What is the balloon car’s speed? Show your work-don’t forget units!

Speed = Distance Time

Speed = 200 cm = 4 cm/s 50 s

22. Mandy’s balloon car travels at a speed of 20 m/s for 10 s. What is the distance that the balloon car traveled? Show your work-don’t forget units!

Speed = Distance Time

20 m/s = Distance = 20 X 10 10 s

Distance = 200 m

23. What is the difference between speed, velocity, and acceleration? 

Speed – describe how much distance an object travels in a period of time (3m/s) distance/time

Velocity – speed with direction (3 m/s, North) Acceleration – Acceleration is a change in velocity by; changing

speed (starting, stopping, speeding up, or slowing down) or changing direction (m/s2)Acceleration = change in velocity/time

24. Create a graph that shows constant motion. What is constant speed?

Constant motion - it has the same increase in speed in a given time period

25. Create a graph that shows an object at rest.

26. Create a graph that shows two runners running at a constant speed; one running slightly faster than the other.

27. Create a graph that shows an object gradually speeding up

28. Create a graph that shows a student riding their bike home from school. After 5 minutes it starts to rain lightly, so the student rides a little faster. After another 2 minutes it starts to rain hard, and the student speeds the rest of the way home. The total time the student takes to get home is 10 minutes.