Work and Machines

1
Work and Machines

• Final Review

2

• Nancy pushed a box with a force of 45 N for 15m.
  How much work did Nancy do?

3
Answer

• 675J

4

• The force that you apply to a machine is the?

5
Answer

• Input Force

6

• When casting a fishing pole you need to apply 10N
  of force. The pole in return will put out 30N of
  force. Calculate the mechanical advantage of the
  fishing pole?

7
Answer

• 30N/10N 3

8

• The mechanical advantage of a machine is the
  number of times a machine increases

9
Answer

• The force exerted on the machines

10

• What is the ideal mechanical advantage of an
  incline plane that is 6.0 m long and 1.5 m high?

11
Answer

• 6.0/1.5 4.0

12

• An ideal machine would have an efficiency of what?

13
Answer

• 100

14

• The ideal mechanical advantage for an inclined
  plane is equal to the length of the inclined
  plane divided by the what?

15
Answer

• Height

16

• Pulling down on a rope to hoist a sail on a
  sailboat is an example of a machine that does
  what?

17
Answer

• Changes the direction over which a force is
  exerted.

18

• The ideal mechanical advantage of a wheel and
  axle is equal to the

19
Answer

• Radius of the wheel divided by radius of axle

20

• If tight, rusty scissors have an efficiency of 50
  , half of your work is wasted do to what?

21
Answer

• Friction

22

• What is the formula used to calculate the
  efficiency of a machine.

23
Answer

• Output work/inputwork x 100

24

• A ramp is an example of a simple machine called
  what?

25
Answer

• Inclined plane

26

• Which of these is an example of a third-class
  lever?

27
Answer

• Your elbow

28

• If the radius of a doorknob is 6.0 cm and the
  radius of its inner rob is 2.0 cm, what is the
  mechanical advantage?

29
Answer

• 6.0/2.03

30

• A machine that utilizes two or more simple
  machines is called a what?

31
Answer

• Compound Machine

32

• You do 5,000 J of work using a sledge hammer.
  The sledge hammer does 2,000J of work on the
  spike. What is the efficiency if the sledge
  hammer?

33
Answer

• 40

34

• One example of a compound machine is a?

35
Answer

• Bike, car, any thing that uses a variety of
  simple machines.

36

• Which of the following describes a first class
  lever?

37
Answer

• -----------/\--------------
• Fulcrum is in the middle

38

• A(n)_________ is a grooved wheel with a rope,
  chain or cable running along the groove.

39
Answer

• Pulley

40

• Which of the following simple machines is an
  inclined plan wrapped around a post?

41
Answer

• Screw

42

• If you exert a force of 20 newtons to push a desk
  10 m, how much work do you do on the desk?

43
Answer

• 200J

44

• If a pulley is attached to something that doesnt
  move, is called what?

45
Answer

• Fixed pulley

46

• The fixed point that a lever pivots around is
  called the

47
Answer

• Fulcrum

48

• A machine can do any of the following except..

49
Answer

• Increase work

50

• How does a ramp make it easier to move a heavy
  object a certain distance?

51
Answer

• It decreases the amount of force required to move
  the object.

52

• When you raise or lower a flag on a flagpole, you
  are using a (n)

53
Answer

• Pulley

54

• What do machines do?

55
Answer

• Change amount of force you exert or the distance
  over which you exert the force.

56

• Which of the following equations should be used
  to calculate work done?

57
Answer

• WFxD

58

• Power is measured in units called

59
Answer

• Watts

60

• The power of a light bulb that converts
  electrical energy at a rate of 100J per second is
  what?

61
Answer

• 100 Watts

62

• ______ is the rate at which work is done.

63
Answer

• Power

64

• If you apply a force of 10N to a box and push it
  10 m in 10 s, how much power did you deliver?

65
Answer

• 10 Watts

66

• For work to be done on an object

67
Answer

• Object must move in the same direction as the
  force applied

68

• Which of these is an example of work being done
  on an object.

69
Answer

• Pushing an object across the room

70

• Work is measured in what?

71
Answer

• Joules

72

• If you exert a force of 15 N to push a desk 20 m,
  how much work do you do on the desk?

73
Answer

• 300J

74

• ________ is the rate at which work is done.

75
Answer

• Power