5th Class Science Work, Force, Energy and Simple Machines Simple Machines

     Simple Machines

Machines are simple tools which make our work easier and faster. They help us to do many work.

Some example of simple machines are lever, inclined plane, wheel and axle, pulley and screw.

           Levers

Levers are commonly used tools like scissors, hammers and screw drivers.

When we life a rock with the help of a rod, the weight lifted by the person is the load and the force with which it is lifted is the effort. The point of contact of rod and the stone is the fulcrum.

Levers can be classified according to the portion of the fulcrum, the load and the effort.

When the fulcrum lies between the load and the effort, is called first class lever.

When the load is in between the fulcrum and the effort, it is a second class lever. When the effort is in between the fulcrum and the load, it is a third class lever.

          Inclined Placed

An inclined place is a slope which makes work easier. When workers have to load or unload a truck they use a plane of wood as an inclined plane.

           The Pulley

A pulley is a small wheel with a groove around its outer edge. There are two types of pulleys a fixed pulley and a movable pulley. The pulley used for drawing water from a well is a fixed pulley movable pulleys along with fixed pulleys are used to lift loads.

          The wheel and axle

A wheel attached with a rod attached to it is known as a what-and axle arrangement. It is easier to push a load on wheels than carrying it. This arrangement is used in vehicles. Sewing machines and cycles.

           The Screw

Screw is a tool used to gold things tightly together. Bigger screws called screw jacks are used to lift cars and other heavy objects. When two things are joined by a screw, they are held together through a long distance while when we join things with a nail, they are held together only through the length of the nail.

      Consider the following statements:

Statement: 1. Energy is the capacity to do work.

Statement: 2. Energy is the exerted force on a body.

Which one of the following is correct about the above statements?

(a) Both statements are true

(b) Both statements are false

(c) Statement 1 is true and 2 is false

(d) Statement 1 is false and 2 is true

(e) None of these

Answer: (c)

Explanation 

Energy is the capacity to do work. Therefore, option (C) is correct and rest of the options is incorrect.

     Which one of the following types of energy is possessed by a body when placed at a certain height?

(a) Kinetic energy

(b) Potential energy

(c) Heat energy

(d) Sound energy

(e) None of these

Answer: (b)

Explanation

When a body is placed at a certain height, body possesses potential energy. Therefore, option (B) is correct and rest of the options is incorrect.

Unit for the measurement of work done is Joule.

Work done = Force x Displacement.

Work is not done if body does not change its position or shape on force applied to it.

Potential energy is the product of mass, gravitational constant and height from the surface of the earth of the body.

The formula to calculate the kinetic energy  .