Question

6.

What is the difference in work needed to push a 100 kg crate (at constant speed) a

distance of 2 m along an inclined plane that is at an angle of 20 degrees with the

horizontal, if the coefficient of kinetic friction was equal to 0.20 or zero?

Answer 1

here,

mass of carte , m = 100 kg

s = 2 m

theta = 20 degree

when uk = 0.2

and it is moving at constant speed

the net force is zero

and the net work done on system is zero

the work done , W1 = m * g * s * sin(theta) + uk * m * g * s * cos(theta)

W1 = 100 * 9.81 * 2 * (sin(20) + 0.2 * cos(20))

W1 = 1039.8 J

when uk = 0

and it is moving at constant speed

the net force is zero

and the net work done on system is zero

the work done , W2 = m * g * s * sin(theta)

W2 = 100 * 9.81 * 2 * (sin(20))

W2 = 671.04 J

the difference in work done dW = W1 - W2 = 368.76 J