Download Document

Forces Test Review
Review these problems and the Chapter 3 Reading guide.
Newton’s three laws of motion:
1) Describe Newton’s first law of motion and give some examples.
2) Describe Newton’s third law of motion and give some examples.
3) What is Newton’s second law of motion? Write
the equation and explain what it means in your
own words.
4) If acceleration is in m/s/s and mass is in kg, then
the units of force will be ____________
F=MA
5) Look at the diagram at the left. How will the
acceleration of these two carts compare?
Figure A
Explain using Newton’s second law.
6) For the lab illustrated in the last question, Calder collected the following
data at right (note: he did not measure very carefully and just guessed on
a few of them). Describe what is wrong with his data, then create a data
table which shows a more believable set of data.
7) Which set of data below best agrees with Newton’s second law?
Figure B
Force
(n)
100
200
300
400
500
Acceleration
(m/s/s)
0.25
1.00
2.00
4.00
6.00
8) Match line a and b to the correct cart below. Explain why you made your choices. (note: the big red
block on the second diagram below represents a heavy, 1kg weight.)
1
9) A baseball pitcher exerts a force of 22 N on a baseball while throwing a fastball. The baseball has a
mass of 0.145 kg. What is the ball’s acceleration?
10) If 80 N is required to cause a bicycle to accelerate at 2 m/s/s, what is the mass of the bicycle?
11) If a 60 kg person pushes backwards against the ground with a force of 100N, what will his forward
acceleration be?
12) How much force is required to accelerate a 40 kg cart at 8m/s/s?
13) A boy running down a hill accelerates 0.8 m/s/s. Assuming the boy exerts a force of 28N when he
plows into his friend, how much mass does the boy have?
14) A force of 3.7 N is applied to a 550 g rock. What is the rock’s acceleration in m/s/s?
Using F=MA and A=V/T together:
15) A catcher catches a 42 m/s fastball from a pitcher and brings it to rest
in 0.3 s. How much force does the catcher exert on the 0.145 kg ball to bring it to rest?
16) A 250 kg sail boat moving at 10.0 m/s suddenly catches a cool breeze which increases its speed to
20.0 m/s in 10.0 s. With how much force is the wind pushing against the sail boat?
17) A bus travels from 0 m/s to 2.7 m/s in 5 seconds at which time the bus then hits a fire hydrant.
Assuming the bus has a mass of 12,720 kg, how much force is exerted on the fire hydrant?
Conceptual / Misc:
18) How much force is required to keep a 100,000 kg spaceship moving at 25,000 mi/h out in space
where there are no other forces besides the force from the ship's rockets?
19) Define static equilibrium and dynamic equilibrium. Describe two examples of each.
2
F-Net Problems and free body diagrams
20) At a certain instant in time, the engine of a 7,000 kg truck is causing a forward force on the truck of
5,000 N while the friction against the truck is 500 N.
a. Draw a free body diagram to show the forces on the truck.
b. What is the Net Force acting on this truck?
c. What is the acceleration of this truck?
21) Jimmy has a mass of 50 kg and is skating down tha sidewalk by pushing backwards on the ground
with a force of 125 Newtons. He is experiencing 30 Newtons of rolling friction and 10 Newtons of
air resistance.
a. Draw a free body diagram to show the forces on Jimmy.
b. What is the Net Force acting on Jimmy?
c. What is Jimmy’s acceleration?
22) The engines of a 50,000 kg jet airplane are exerting a force of 130,000 N while the airplane is
experiencing an average air resistance of 25,000 N.
a. Draw a free-body diagram showing all the forces on the airplane.
(note: the plane is traveling to the right).
b. What is the Net Force (Fnet) on the airplane?
c. What is the acceleration of the airplane?
23) Draw Free-Body diagrams for the following situations:
 A spaceship is sitting on the launch pad motionless
 A spaceship blasting off and accelerating upwards.
 The spaceship is traveling through space at a constant speed and is not near any gravitational
field.
 A spaceship has lost a rocket engine and is being slowed down by Earth’s gravity.
24) Draw Free-Body diagrams for the following situations:
 A car parked in a level parking space.
 A car accelerating as it enters the highway.
 A car slowing down as it applies its brakes.
 A car travelling along the highway at a constant velocity.
Some More Thinking about F= MA (also known as A = F/M)
25) If the net force on an object is doubled, its acceleration will ____________ double
26) If the mass of an object is doubled, the acceleration will _______________________________
27) What will happen to the acceleration on an object if we double both the mass and the net force acting
it? Explain.
28) Look at the diagram below then answer the following:
A
20 kg
B
Fapp = 10 N
40 kg
C
Fapp = 10 N
20 kg
D
Fapp = 20 N
40 kg
Fapp = 20 N
a) Which object will have the greatest acceleration?
b) Which object will have the least acceleration?
c) Which two objects will have the same acceleration?
3