Question

The velocity of a particle at an instant is $10m/s$. After $5$ sec, the velocity of the particle is $20m/s$. Find the velocity at $3$ sec before from the instant when velocity of a particle is $10m/s$. (Assume acceleration is constant throughout the journey.)

• A. $8m/s$
• B. $4m/s$
• C. $6m/s$
• D. $7m/s$

Answer 1

The correct option is B $4m/s$

Given, $u=10m/s$, $t=5sec$, $v=20m/s$, $a=?$

so, acceleration $=a=\frac{20-10}{5}=2ms{}^{-2}$

For 3 seconds before,

Using $v_1=u_1+at$, or $10=u_1+2\times 3$ or $u_1=4m/s$