A child applies a force F parallel to the x-axis to block moving on a horizontal surface. As the child controls the speed of the block, the x-component of the force varies with the x-coordinate of the block as shown in figure. calculate the work by the force F whin the block moves.
.
(a) from `x =0` to `x =3.0m`
(b) from `x =3.0 m` to `x =4.0m`
(c) from `x =4.0 m` to `x =7.0 m`
(d) from `x =0` to `x =7.0 m`.

Answer

A, B, C, D

Explanation

(a) From `x =0` to `x =3.0m`
`S = + ve`
`F = +ve`
`:. W_(1) = + "Area"`
`= +4J`
(b) Form `x =3 m` to `x =4 m`
`F = 0 rArr W_(2)=0`
(c ) From `x =4 m` to `x =7 m`
`S = + ve` and `F= -ve`
`:. W_(3) = +"Area" = +1J`
(d) From `x = 0` to `x =7 m`
`W=W_(1) + W_(2) + W_(3) =3J`.