Test Review

1
Test Review

• Chapter 4 5

2
Questions
Why is work output for a machine is always less
than the work input?

• 1. Why is work output for a machine always less
  than the work input?

Some of the work is used to overcome friction

• 2. Give two example of a wheel and axle

Door knob, Ferris Wheel, Steering wheel, Faucet
handle, etc.
3
Questions
Why is work output for a machine is always less
than the work input?

• 3. Power is defined as

How fast work is being done

• 4. You apply 200 N to a machine and the machine
  applies 2,000 N to an object. What is the
  mechanical advantage?

MA2000N / 200N10
4
Questions
Why is work output for a machine is always less
than the work input?
small

• 5. When you turn a screw, you apply a ________
  force over a _______ distance while the screw
  applies a _______ force over a ____________
  distance.

long
large
short

• 6.Draw a second-class lever label where the
  fulcrum, input force and load are.

5
Questions
Why is work output for a machine is always less
than the work input?

• 7. An object is in projectile motion if?

It is thrown with a horizontal push, it is
pulled down by gravity and it does not accelerate
horizontally
8.Complete this sentence. Newton's third law of
motion states that whenever one object exerts a
force on a second object
Another force occurs that is equal in size and
opposite in direction
6
Questions
Why is work output for a machine is always less
than the work input?

• 9.Parachutes slow skydivers to a safer terminal
  velocity because

Increase air resistance
10.Terminal velocity is reached when the net
force on a falling object reaches
zero Newton's
7
Questions
Why is work output for a machine is always less
than the work input?

• 11.Hammering a nail into wood is an example of
  using which simple machine?

3rd class lever
12. Explain the force distance trade off
As one increases the other decreases
8
Questions
Why is work output for a machine is always less
than the work input?

• 13. Which of the following machines is the MOST
  efficient?
•  
• a machine in which you input 4 J of work and it
  outputs 3 J of work
•  
• a machine in which you input 12 J of work and it
  outputs 6 J of work

3J / 4J .75 x 100 75
6J / 12J .5 x 100 50
14.Name a game that uses conservation of momentum?
Billiards, bowling , baseball
9
Questions
Why is work output for a machine is always less
than the work input?

• 15.When using a fixed pulley describe the force
  distance relationship.

It changes the direction of the force
16. ________________decreases as the mass of the
object increases, increases as the force on the
object increases, and is in the same direction as
the net force on the object.
Acceleration
10
Questions
Why is work output for a machine is always less
than the work input?

• 17.Does a 40W light bulb or a 100W light bulbs do
  the most work each second?

100W
 18.Which of the following could be a machine's
mechanical efficiency? (95 Nm) (95 J/s) or (95)
95
11
Questions
Why is work output for a machine is always less
than the work input?

• 19.Levers are divided into classes according to
  the location of what 3 things?

Fulcrum, input force load (output force)
20.If you do 50 J of work in 5 s, your power is
50J / 5s 10W
12
Questions
Why is work output for a machine is always less
than the work input?

• 21.Newton's second law of motion states that an
  object's acceleration _______________ as its mass
  decreases and as the force acting on it
  __________________.
•  

increases
increases
You have four vehicles, all driving at the same
velocity side-by-side on a four-lane highway.
They are a fully-loaded truck, an empty truck, a
midsize van, and a small car.   22.Which one has
the MOST momentum?
Fully loaded truck
13
Questions
Why is work output for a machine is always less
than the work input?

• 23.If all the vehicles brake at the same time
  because there is a collision ahead, which one
  will come to a complete stop FIRST?
•  

Small car
24. Define machine
A device that makes work easier by changing the
size or direction of the force
14
Questions
Why is work output for a machine is always less
than the work input?

• 25.Air resistance is
•  

Fluid friction that opposes the motion of an
object through air
26.Use Newton's second law of motion to calculate
the acceleration of a 7 kg mass if a force of
68.6 N acts on it?
A F/m 68.6N / 7kg 9.8m/s/s or 9.8 m/s2
15
Questions
Why is work output for a machine is always less
than the work input?

• 27.Complete this sentence. Newton's third law of
  motion states that if a force is exerted on an
  object, another force occurs that  

Is equal in size and opposite in direction
28.Getting regular oil changes for your car
improves the car's
Mechanical efficiency
16
Questions
Why is work output for a machine is always less
than the work input?

• 29.Galileo proved that the rate at which an
  object falls 

Is not affected by the mass
30.If a machine has a work input of 8 N and gives
work output of 6 N, what is this machine's
mechanical efficiency?
6N / 8N .75 x 100 75
17
Questions
Why is work output for a machine is always less
than the work input?

• 31.Give an example of an object in projectile
  motion is
•  

Leaping frog, ball thrown horizontally
32.When a machine changes the size of a force,
the __________________________ must also change.
Distance of the force
18
Questions
Why is work output for a machine is always less
than the work input?

• 33.A ramp is an example of which simple machine?
•  

Inclined Plane
34.____________ changes in size or direction when
done by a machine.
Force
19
Questions
Why is work output for a machine is always less
than the work input?

• 35. Which lever result in an output force less
  than the input force.
•  

3rd class or 1st class with fulcrum near input
force
36.A man applies a force of 500 N to push a truck
10 m down the street. How much work has been done?
500N x 10m 5000J
20
Questions
Why is work output for a machine is always less
than the work input?

• 37.What is the mechanical advantage of an
  inclined plane 3 m long and 0.5 m high?
•  

3m / .5m 6
38.Give an example of a second-class lever?
Wheel barrow
21
Questions
Why is work output for a machine is always less
than the work input?

• 39.Complete this law. According to Newton's
  first law of motion, a moving object that is not
  acted on by an unbalanced force will  

Remain in motion
40.Explain the Conservation of Momentum using
figure 21 page 99.
The action force makes the billiard ball move as
the reaction force makes the cue ball stop
22
Questions
Why is work output for a machine is always less
than the work input?

• 41.Draw and label a movable pulley
•  

42.Inertia is used when explaining Newton's
__________ law of motion.
1st
23
Questions
Why is work output for a machine is always less
than the work input?

• 43.Which type of lever(s) can provide a
  mechanical advantage of greater than 1?

2nd class or 1st class with fulcrum closer to the
load
44.All objects accelerate toward the Earth at a
rate of 9.8 m/s/s. This means that for every
second that an object falls, its downward
velocity ____________________________.
Increases by 9.8 m/s
24
Questions
Why is work output for a machine is always less
than the work input?

• 45.Explain the action and reaction force used as
  a swimmer swims through the water.

• The action force is the hands and feet
• The reaction force is water pushing on hands
  feet
• The reaction force moves the swimmer forward

25
Questions
Why is work output for a machine is always less
than the work input?

• 46.Work is being done when

A force causes an object to move in the direction
of the force
47.A ball is dropped from a rooftop. What is the
ball's velocity after 3 s? (Assume that there is
no air resistance.)
9.8 m/s/s x 3s 29.4m/s
26
Questions
Why is work output for a machine is always less
than the work input?

• 48.The unit for work is the __________.

Joule
49.A golf ball and a bowling ball are moving at
the same velocity. Which has more momentum and
why?
Bowling ball it has more mass
27
Questions
Why is work output for a machine is always less
than the work input?

• 50.When using a fixed pulley describe the
  relationship between input and output forces.

The forces are equal but the forces are in
opposite directions
51.Which has the greatest mechanical
advantage? a machine to which you apply a force
of 50 N and the machine applies a force of 150
N   a machine to which you apply a force of 60 N
and the machine applies a force of 200 N
150N / 50 N 3
200N / 60N 3.3
28
Questions
Why is work output for a machine is always less
than the work input?

• 52. Your muscles and bones form what type of
  simple machine?

Lever
53.The amount of air resistance acting on an
object depends on the object's
Size and shape
29
Questions
Why is work output for a machine is always less
than the work input?

• 54.If three balls of different materials were
  dropped at the same time from the same height,
  which would hit the ground first? (Assume there
  is no air resistance.)

They would all hit at the same time
55.Mechanical efficiency of compound machines is
often ________ because of friction.
low
30
Questions
Why is work output for a machine is always less
than the work input?

• 56.Which of the following actions do more work on
  an object?
• lifting an 80 N box 1 m up off the floor
• lifting a 160 N box 1 m up off the floor

80N x 1m 80J
160N x 1m 160J
57.The unit for power is the _________?
watt
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