Question

a boy is pulling a cart by supplying a constant force of 8N on a straight path of 20m.On a round about of 10m diameter he forgets the path and takes 1 1/2 turns and then continues on the straight path for another 20m.Find the network done by the boy on the cart.

Answer 1

Work Done in covering 20 m when constant force of 8N is applied 

we know 

W = F  x s 

=> W1 = 8 x 20 = 160 J 

Now distance covered in one and half circle (diameter = 10m) 

radius = 5 m 

Distance covered in one circle 

= 2 πr = 2 x 3.14 x 5 = 31.4 m

Distance covered in half circle 

= πr = 3.14 x 5 

= 15.7 

distance covered in one and a half circle 

= 15.7 + 31.4 = 47.1 m 

Now , 

Workdone will be 

W2 = 8 x 47.1 = 376.8 J 

Travelling again for 20 m 

W3 = 20 x 8 = 160 J 

Total work done 

W1 + W2 + W3 

160 + 376.8 + 160 

= 696.8 ≈ 697 Joules