Question

The speed of a car changes from 0 to $5m{s}^{-1}$ in the first phase and from $5m{s}^{-1}$ to $10m{s}^{-1}$ in the second phase and from $10m{s}^{-1}$ to $15m{s}^{-1}$during the third phase. In which phase the increase in kinetic energy is more?

• A. First phase
• B. Second phase
• C. Third phase
• D. Same in all the three phases

Answer 1

The correct option is C Third phase

$\Delta {(K.E)}_I=\frac{1}{2}m\times (5^2-0^2)=\frac{25m}{2}$

$\Delta {(K.E)}_{II}=\frac{1}{2}m\times ({10}^2-5^2)=\frac{75m}{2}$

$\Delta {(K.E)}_{III}=\frac{1}{2}m\times ({15}^2-{10}^2)=\frac{115m}{2}$