A body of mass 2kg is resting on a rough horizontal surface. A force of 20N is now applied to it for 10s, parallel to the surface. If the coefficient of kinetic friction between the surfaces of contact is 0.2. Calculate change in kinetic energy of the object in 10s. (Take g=10ms^(-2)).

A body of mass 2kg is resting on a rough horizontal surface. A force o

1.	A body of mass 2kg is resting on a rough horizontal surface. A force of 20N is now applied to it for 10s, parallel to the surface. If the coefficient of kinetic friction between the surfaces of contact is 0.2. Calculate change in kinetic energy of the object in 10s. (Take g=10ms^(-2)).
Answer» Solution :Mass = 2kg Initial velocity `u=0` Force `F=2N` Coefficient of kinetic friction `mu_(k)=0.2` Time `t=10s` `f_(k)=mu_(k)mg` `=0.2xx2xx10=4N` NET force `F'=f-f_(k)` `=20-4=16N` Acceleration, `a=(F')/(m)=(16)/(2)=8MS^(-1)` Distance covered `s=ut+(1)/(2)at^(2)` `s=0+(1)/(2)xx8xx(10)^(2)=400m` Change in kinetic energy = WORK DONE by the net force `W_(2)=F's` `=16xx400=6400J`