Question

An eraser weighing $2$ $N$ is pressed against the black board with a force of $5$ $N$. The coefficient of friction is $0.4$. How much force parallel to the black board is required to slide the eraser upwards?

• A. $2N$
• B. $2.8N$
  
• C. $4N$
• D. $4.8N$

Answer 1

The correct option is C $4N$

Total downward force acting on eraser,
$=$ Frictional force $+$ weight
This is the minimum amount of force required to lift the eraser upwards
$=5\mu +2=4N$