# Work, Power, And Efficiency Question Preview (ID: 60983)

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Concept And Calculating Work Power And Efficiency.
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**If two objects do the same amount of work, but one does it in less time.**

a) The heavier one has more power.

b) The slower one has more power.

c) The faster one has more power.

d) The lighter one has more power.

**A father lifts his daughter repeatedly in the air. How much work does he do with each lift, assuming he lifts her 2.0 m and exerts an average force of 190 N?**

a) 380 J

b) 95 J

c) 380 W

d) 95 W

**____the rate at which work is done.**

a) Work

b) Efficiency

c) Power

d)

**___the ratio of work output to work input.**

a) Work

b) Efficiency

c) Power

d)

**___cannot be greater than ___ due to friction.**

a) Efficiency, 100%

b) Efficiency, 0%

c) Work out, Efficiency

d) Work in, Efficiency

**If you set the object on a table, does the table exert a force on the object?**

a) yes

b) no

c)

d)

**___cannot be greater than ___ due to friction.**

a) Work in , Work out

b) Work out, Work in

c)

d)

**When you hold something, are you exerting a force on the object?**

a) yes

b) no

c)

d)

**When you hold something, are you doing work?**

a) yes

b) no

c)

d)

**Work =**

a) force ·time

b) force ·distance

c) time ·distance

d) force ·gravity

**Work is done when a _____ is exerted on an object and the object moves a _____.**

a) force, force

b) force, time

c) distance, force

d) force, distance

**A watt is the amount of power required to**

a) do 1 J of work in 1 s.

b) move 1 kg over 1 m

c) do 1 W of work in 1 s

d)

**A weight lifter does 686 J of work on a weight that he lifts in 3.1 seconds. What is the power with which he lifts the weight?**

a) 221 W

b) 2126.6 W

c) 0.0045 W

d)

**Mechanical advantage is**

a) the ratio between effort force and efficiency force

b) the ratio between input force and output force

c) the ratio between output force and input force

d)

**A roofer needs to get a stack of shingles onto a roof. Pulling the shingles up manually used 1549 N of force. Using a system of pulleys requires 446 N. What is the mechanical advantage?**

a) 347

b) 3.47

c) 0.29

d) 29%

**What is the efficiency of a machine if 55.3 J of work are done on the machine, but only 14.3 J of work are done by the machine?**

a) 25.9 J

b) 0.259%

c) 25.9 %

d) 386%

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