Question

a block of mass 10kg is kept over a rough surface and a force F = 4t is applicable on it . at what value of t the block will start??​

Answer 1

Answer:

to just start moving. force applied should be equal to frictional force. so

frictional force = Force

i.e.μmg = 4t

0.4×10×10=4t

t=10

Answer 2

Answer:

At t =10 seconds block starts moving.

Explanation:

Given in the problem is a block of mass 10kg kept on a rough surface with coeeficient of friction  μ=0.4.

A variable time dependent force of 4t Newton is applied to it,

Block will start moving when the magnitude of the applied force exceeds the value of static frictional force acting on the body,

$F_{applied}\geq F_{frictional}$                            

4t ≥ μmg

$4t \geq 0.4*10*10\\t \geq 10\ seconds$

Hence, at t =10 seconds block starts moving.