A 40kg crate is pulled 40m along a horizontal floor by a constant force exerted

Question

A 40kg crate is pulled 40m along a horizontal floor by a constant force exerted by a person FP = 100N, which acts at a 370 angle as in the picture below.

If the velocity is constant, determine the work done by

A) The force of the person pulling.

B) The gravitational force exerted by earth.

C) The normal force.

D) The frictional force

E) Calculate the total work. Show your work.

F) The pulling force of the person is increased to 125 N. The coefficient of kinetic friction is µk = 0.20 Find the acceleration of the box.

G) Find the work done by each force below when the force of the person is at 125 N. The box is pulled a distance of 2.5 m.

a) Gravitational force exerted by earth

b) Normal force

c) Frictional force

d) Force of the person

e) Calculate the total work done

Explanation / Answer

Here ,

angle of pulling , theta = 37 degree

A) work done by person = F * d * cos(theta)

work done by person = 100 * 40 * cos(37)

work done by person = 3194 J

B) as the floor is horizontal ,

work done by gravitational pull = 0 J

c)

as normal force is perpendicular to direction of motion

work done by normal force = 0 J

d)

as the velocity is constant ,

net work done on the box is zero

work done by frictional force = -work done by person

work done by frictional force = -3194 J

E)

Using work energy theorum

Total work done = change in kinetic energy

as velocity is constant

Total work done = 0 J

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