Question

A wedge of mass 10kg is moving rightwards. A block of mass $10kg$ is placed on it. Friction coefficient between wedge and block is $0.8$. Then,
$[takeg=10m/s^2]$

• A. If wedge is moving with constant velocity then friction acting on block is 64N
• B. If wedge is moving with constant velocity then acceleration of block is zero
• C. If wedge is moving with a $=2\hat{i}m/s^2$ then friction acting on block is 44N
• D. If wedge is moving with $a=10\hat{i}m/s^2$ then friction is zero

Answer 1

Answer: (B), (C)

The correct options are
B If wedge is moving with constant velocity then acceleration of block is zero
C If wedge is moving with a $=2\hat{i}m/s^2$ then friction acting on block is 44N

If moving with constant velocity then a $=$ 0

so friction available $=\mu mg\cos \theta$

$=\left(0.8\right)\left(10\right)\left(10\right)\left(4/5\right)=64N.$

but mgsin $\theta =60N$

so required friction is 60N.

So net force is zero.

and $a=2\hat{i}$

since due to acceleration N > 80, so $f_{available}>64N$

and when $a=10\hat{i}$ then friction is 20N downwards.