Physics
Work and Energy
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#41 In presence of non-conservative forces, mechanical energy:
A) decreases by dissipative work
B) increases always
C) remains strictly constant
D) is undefined
#42 Work done by variable force $F(x)$:
A) $W=\int_{x_1}^{x_2}F(x)\,dx$
B) $W=F\,\Delta x$
C) $W=\dfrac{F}{x}$
D) $W=F^2x$
#43 If $U(x)=\tfrac12 kx^2$, then $F(x)$ is:
A) $-kx$
B) $+kx$
C) $-\tfrac12 kx$
D) $+\tfrac12 kx$
#44 If $K=\tfrac12 mv^2$ and $p=mv$, then $K$ in terms of $p$:
A) $\dfrac{p^2}{2m}$
B) $\dfrac{2p}{m}$
C) $\dfrac{m}{2p^2}$
D) $mp$
#45 Unit of spring constant $k$ is:
A) $\text{N m}^{-1}$
B) $\text{N m}$
C) $\text{N}$
D) $\text{J m}^{-1}$
#46 A $2\ \text{kg}$ mass falling $5\ \text{m}$ (no losses) gains KE:
A) $\approx 98\ \text{J}$
B) $\approx 9.8\ \text{J}$
C) $49\ \text{J}$
D) $490\ \text{J}$
#47 If $U$ decreases by $20\ \text{J}$ and no non-conservative work:
A) $K$ increases by $20\ \text{J}$
B) $K$ decreases by $20\ \text{J}$
C) $K$ unchanged
D) $K$ doubles
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