Question

Energy required to accelerate a car from 10 m/s to 20 m/s compared with that required to accelerate it from 0 to 10 m/s is

• A. twice
• B. thrice
• C. four times
• D. same

Answer 1

Answer: (B)

$E_1=\frac{1}{2}m(v_2^2-v_1^2)$ $\therefore$ $E_1=\frac{1}{2}m[{(20)}^2-{(10)}^2]$ $\Rightarrow$ $E_1=\frac{1}{2}m(400-100)$ $\Rightarrow$ $E_1=\frac{1}{2}m\times 300=150m$ ?(i) $E_2=\frac{1}{2}m[{(10)}^2-0]$ $\Rightarrow$ $E_2=\frac{1}{2}m\times 100=50m$ ?(ii) From Eqs. (i) and (ii), we have $E_1=3E_2$