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8th Grade Mid Term Study Guides > Science Mid Term Study Guide ch 3 > Flashcards

Science Mid Term Study Guide ch 3 Flashcards

1
Q

Chapter 3 Chapter Review

  1. which must be true when work is done

A. no force acts on it
B. an object slows down
C. an object moves quickly
D. an object moves in the same direction as a force exerted on it

A

D

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2
Q

Chapter 3 Chapter review

  1. which must be true when work is done on a resting object and the object moves

A. the energy of the object changes
B. the energyof the object is constant
C. the force on the object is 0
D. the force on the object is constant

A

A

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3
Q

Chapter 3 Chapter review

  1. Which increases the power used in lifting the backpack

A. lifting at a constant speed
B. lifting at an angle
C. Lifting more quickly
D. Lifting a lighter backpack

A

C

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4
Q

Chapter 3 Chapter review

  1. which does more work on an object

A. Pushing a 50N object; 2m dis.
B. pushing 120N object; 7m dis.
C. pushing 150N object; 5m dis.
D. pushing 300N object; 1m dis.

A

B

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5
Q

Chapter 3 Chapter review

which must be true if a machines mechanical advantage is 2

A. Direction of force is changed
B. Output force = input force
C. Output force is greater than input force
D. Output work is greater than input work

A

C

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6
Q

Chapter 3 Chapter review

which ideal mechanical advantage of the pulley system (check book)

A. 1
B. 2
C. 3
D. 4

A

D

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7
Q

Chapter 3 Chapter review

How does friction affect a machine

A. It converts input work into thermal energy.
B. tconverts output work into thermal energy.
C. It converts thermal energy into input work
D. It converts thermal energy into output work

A

A

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8
Q

Chapter 3 Chapter review

which is a simple machine

A. tweezers
B. bicycle
C. can opener
D. car

A

A

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9
Q

Chapter 3 Chapter review

What is the ideal mechanical advantage of the wheel and axle shown below (check book)

A. 1
B. 2
C. 3
D. 4

A

C

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10
Q

Chapter 3 Chapter review

which is most easily used as either a wheel and axle or as a lever

A. ax
B. scissors
C. screwdriver
D. screw

A

C

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11
Q

Chapter 3 Chapter review

Which quantity increases when a frictionless ramp is used to lift an object

A.input force
B. input distance
C. input work
D. output work

A

B

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12
Q

Chapter 3 Chapter review

Contrast the work done when you lift a box with the work done when you carry the box across a room

A

The work done lifting the box equals the weight of the box multiplied by the distance it is lifted. The work done carrying the box equals the force used to move the box horizontally multiplied by the distance moved.

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13
Q

Chapter 3 Chapter review

Does a weight lifter transfer more energy, less energy, or the same amount of energy when lifting the weight faster?

A

The weight lifter would transfer the same amount of energy. regardless of how fast the weight is lifted, because the amount of work would not change.

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14
Q

Chapter 3 Chapter review

First you lift an object from the floor onto a shelf. Then you move the object from the shelf beack onto the floor. Do you preform the same amount of work each time?

A

No. Work is done when lifting an object because the force acts in the same direction as the object’s motion. When the object is lowered, no work is done on it because the applied force is not in the direction of the object’s motion.

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15
Q

Chapter 3 Chapter review

Explain why the output work done by a machine is never greater than the input work to the machine

A

you exert the input force on the machine, the machine changes that force into an output force

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16
Q

Chapter 3 Chapter review

Suggest a reason the efficiency of a machine used in a factory might decrease over time. What could be done to increase the efficiency?

A

The lubricant on the machine might wear off. Adding more lubricant can increase the efficiency.

17
Q

Chapter 3 Chapter review

Imagine useing a screwdriver to drive a screw into a piece of wood. Explain why turning the handle of the screwdriver is easier than turning its shaft

A

it is easier since the large diameter handle multiplies the force applied to it, making it easier to turn the screw

18
Q

Chapter 3 Chapter review

Can you determine if work is being done on the backpack simply by looking at the photo?

A

No because you cannot see how much work is being applied

19
Q

Chapter 3 Standerdize

what is the SI unit of work

A. ampere
B. Joule
C. Newton
D. Watt

A

B

20
Q

Chapter 3 Standerdize

which transfers both k.e and p.e to an object

A. lifting it
B. lowering it
C. pushing it
D. rolling it

A

A

21
Q

Chapter 3 Standerdize

how much work was involved in moving the chair (look at book)

A. 4j
B. 10J
C. 40J
D. 100J

A

D

22
Q

Chapter 3 Standerdize

how much power was used to move the chair (check book)

A. 10W
B. 20W
C. 50W
D. 200W

A

C

23
Q

Chapter 3 Standerdize

what is a 3rd class lever

A. broom
B. hammer
C. nutcracker
D. wheelbarrow

A

A

24
Q

Chapter 3 Standerdize

which correctly completes the m.a equation

A. distance
B. time
C. input force
D. output work

A

C

25
Q

Chapter 3 Standerdize

a simple machine is not able to…

A. change the size of the force
B. Decrease the amount of work required
C. exert an output force on an object
D. make work easier to preform

A

B

26
Q

Chapter 3 Standerdize

which MUST happen in order for work to be done

A. a force must move on an object
B. a machine must transfer force
C. force must be applied on an object
D. output force must exceed input force

A

A

27
Q

Chapter 3 Standerdize

which number represents the output diagram above (check book)

A. 1
B. 2
C. 3
D. 4

A

D

28
Q

Chapter 3 Standerdize

what information is needed to calculate the ideal mechanical advantage of an inclined plane

A. height and length
B. length and thickness
C. thickness and weight
D. weight and width

A

A

29
Q

Chapter 3 Standerdize

which is a characteristic feature of a wedge

A. cable
B. fulcrum
C. slope
D. thread

A

C

30
Q

Chapter 3 Standerdize

what is the difference between simple and compound machines

A

simple machines - machines that do work using only one movement
compound machines - A machine that uses multiple simple machines

31
Q

Chapter 3 Standerdize

Describe a real-life situation in which simple machines would make work easier. Identify 2 machines that would be helpful in the situation and explain how they would be used.

A

Tools like a hammer, screwdriver, saw, etc are simple machines that help a carpenter make furniture

32
Q

Chapter 3 Standerdize

What 2 factors affect the amount of work done on an object? When does a force acting on an object NOT do work? give examples

A

The two factors that affect the amount of work done on object are applied force and the displacement of object. If we apply force on the object, but not cause the displacement of the object, then work is not performed. Example: Holding the weight in same position, we apply force on them but not any displacement

33
Q

Chapter 3 math skills

how much work is do How much work is done when a force of
30 N moves an object a distance of 3 m?

A

W=F/D
W=30N/3M
W=10J

34
Q

Chapter 3 math skills

How much power is used when 600J of work is done in 10s

A

P=w/t
P=600/10
P=60

35
Q

Chapter 3 math skills

How much force would be needed to push a box weighing 30 N up a ramp that has a ideal mechanical advantage of 3? Assume there is no friction.

A

M.A = Wout/Win x 100%
M.A = 10/20 x 100%
M.A = 50%

8th Grade Mid Term Study Guides (2 decks)

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