Question

Force acting on a block versus time graph is shown in figure. Choose the correct options. (Take $m=2kg$ and $g=10{ms}^{-2}$)

• A. At $t=2s$, force of friction is $2N$
• B. At $t=8s$, force of friction is $8N$
• C. At $t=10s$, acceleration of block is $2{ms}^{-2}$
• D. At $t=12s$, velocity of block is $8{ms}^{-1}$

Answer 1

The correct option is A At $t=2s$, force of friction is $2N$

From graph

Friction force $F_r=\mu mg=0.3\times 2\times 10=6N$

Limiting value of friction is $6N$

And value of force increases with time, at slope $=\frac{Force}{time}=\frac{10-0}{10-0}=1(for0<t<10)$

Means after $6\sec ,whenforce\ge 6N$ block start to move.

Hence, at $2\sec$, friction force equal to $2N$.