A machine lifts a load of 100N through a vertical distance of 2m in seconds. What is the work done by machine?

Explanation:

In this chapter, we will study the important concepts of kinetic energy and the

closely related concept of work and power.

A- Kinetic Energy

Kinetic energy is a physical quantity, which is associated with the moving objects

and defined as:

K = ½ mv2

If the body is stationary (v=0), its kinetic energy is zero. The SI unit of kinetic

energy is kg.m2

/s2

or Joule (J), where 1 J=1 kg.m2

/s2

. Kinetic energy is a scalar

quantity.

B- Work

The work is defined as the ability to perform a force along a certain displacement.

There are different types of work as follows:

1- Work done by a constant force

The work done by the constant force F is given by the scalar product of the force F

and the displacement d.

WF = F.d = Fd cosθ

where θ is the angle between the force and displacement. The above equation means

that the work is the product of the displacement magnitude by component of the

force parallel to the displacement. Therefore, work is a scalar quantity (only

magnitude, no direction) and can be positive, negative, or zero. The SI unit of work

is (N.m) or joule (J) where 1 N.m = 1 J.

Special cases and remarks:

• If the angle between the force and displacement is zero (parallel), the work is

WF = F d (maximum work)

d.7.5cm is your answer

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