Question

A car of mass m moving along a circular track of radius r with a speed v which varies with time t as v=kt, k being a constant. Then,

• A. The instantaneous power delivered by the centripetal force is
• B. The power delivered by the centripetal force is zero
• C. The instantaneous power delivered by the tangential force is mt
• D. The power delivered by the tangential force is zero

Answer 1

Answer: (B), (C)

The correct options are
B

The power delivered by the centripetal force is zero

C

The instantaneous power delivered by the tangential force is mt

Centripetal forces $F_c$ = $\frac{m{v}^2}{r}$ = $\frac{m{k}^2{t}^2}{r}$

P = ${\overrightarrow{F}}_c$.$\overrightarrow{v}$ = 0

$F_t=m\left(\frac{dv}{dt}\right)=m\frac{d}{dt}\left(kt\right)=mk$

P = $F_t$.$\overrightarrow{v}$ = m$k^2$t