A block of 7 kg is placed on a rough horizontal surface and is pulled through a variable force F(in N) =5t, where 't' is time in second, at an angle of `37^(@)` with the horizontal as shown in figure. The coefficient of static friction of the block with the surface is one. if the force starts acting at t=0 s, find the time at which the block starts to slide. (Take `g=10 m//s^(2)`)

Explanation

The block begins to side if
`F cos 37^(@)=mu(mg-F sin 37^(@))`
`5t [cos 37^(@)+mu sin 37^(@)]=mu mg`
`5t[(4)/(5)+(3)/(5)]=70` or `t=10` second