1. Machines and Simple Machines:

(i) A machine is a device through which a force applied at one point overcomes resistance at some other point.

(ii) Machines can change the point of application of a force, change the direction in which a force is applied, change the magnitude of the required force, and change the speed of the point of application of a force.

(iii) The main categories of machines are lever, wedge, screw, wheel and axle, and pulley.

2. Lever:

(i) A lever is a rigid body capable of rotating about a point on itself. The fulcrum of a lever is the point about which it can rotate.

(ii) The effort is the force applied to a machine, and the load is the resistance (force) overcome by a machine.

(iii) There are three classes of levers. A class-one lever has the fulcrum in the middle, e.g., scissors. A class-two lever has the load in the middle, e.g., bottle-opener. A class-three lever has the effort in the middle, e.g., the forearm.

3. Inclined Plane:

An inclined plane or ramp is a slope along which loads can be moved by rolling or sliding. It does not satisfy the definition of a machine.

4. Wedge:

A wedge consists of two inclined planes put together. It acts as a machine.

5. Screw:

A screw is a nail with grooves or threads going around it. Jacks used to lift cars, and vices work on the principle of the screw.

6. Wheel and Axle:

A wide handle or wheel fixed to a rod is called a wheel-and-axle arrangement. The rod is called the axle. The wider object fixed to the axle is called the wheel.

7. Pulley:

A pulley is a wheel or disc which can rotate freely about its axle. It can change the point of application and direction of the effort.

8. Mechanical Advantage:

(i) The mechanical advantage $(MA)$ of a machine is defined as the ratio of the load to the effort. It may also be defined a. the ratio of the distance moved by the effort arm to the distance moved by the load arm.

(ii) Depending upon whether the mechanical advantage is greater than, less than or equal to $1$ , a machine works as a force multiplier, produces gain in speed or changes the direction of the effort respectively.

The single fixed pulley helps us to multiply force.

Important Questions on Simple Machines

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