Question

a child pushes a toy cart from rest on a smooth horizontal surface with a force F=5N, directed at an angle ø =10° below the horizontal. calculate the work done by the child in 5s if the carts mass is m=5kg

Answer 1

Horizontal force = $F\ cos\phi=5 \ cos 10\degree = 4.92\ N$

If $a$ be the horizontal acceleration then

$ma=horizontal \ force\\ 5a=4.92\\ a=0.984\ m/s^2$

Distance traveled in t seconds with uniform acceleration $a$ is given by

$s=ut+\frac{1}{2}at^2$

Here u= initial velocity = 0 (since the cart start from rest)

Putting t = 5 s we get

$s=0+\frac{1}{2}\times 0.984\times 5^2 \ m\\ s=12.3\ m$

Therefore, work done in 5 s is W= Horizontal force x Horizontal displacement

W= 4.92 x 12.3 J

W = 60.5 J

Answer: Work done in 5 s is 60.5 J