Physics
Work and Energy
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#33 Efficiency $\eta$ is:
A) $\dfrac{\text{useful output}}{\text{input}}$
B) $\dfrac{\text{input}}{\text{output}}$
C) $\text{output}\times\text{input}$
D) $\text{output}-\text{input}$
#34 Unit of efficiency is:
A) dimensionless
B) joule
C) watt
D) percent only
#35 If $W=0$ but $F\ne0$, it implies:
A) $\theta=90^\circ$
B) $\theta=0^\circ$
C) $\theta=180^\circ$
D) $\theta=30^\circ$
#36 A body moving in a circle at constant speed has:
A) no work by centripetal force
B) positive work by centripetal force
C) negative work by centripetal force
D) maximum work
#37 Work done by weight during vertical lift by $h$:
A) $-mgh$
B) $+mgh$
C) $0$
D) $2mgh$
#38 $1\ \text{kWh}$ equals:
A) $3.6\times10^{6}\ \text{J}$
B) $3.6\times10^{3}\ \text{J}$
C) $3.6\times10^{5}\ \text{J}$
D) $3.6\times10^{4}\ \text{J}$
#39 If $P=Fv$ and $F$ is constant, then $P$ is proportional to:
A) $v$
B) $v^2$
C) $1/v$
D) $v^0$
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