F. Short Answer Questions

1. Why are machines used?

Machines are used to make our work easier. They help us lift heavy objects, cut things, or move items with less effort. They save time and energy.

2. What is a lever? Name the three types of levers.

A lever is a simple machine made of a rigid bar that pivots around a fixed point called a fulcrum. It is used to lift or move loads with less effort.
The three types of levers are:

• First-class lever: Fulcrum is between the load and the effort (e.g., seesaw).
• Second-class lever: Load is between the fulcrum and the effort (e.g., wheelbarrow).
• Third-class lever: Effort is between the load and the fulcrum (e.g., tweezers).

3. Write a short note on the pulley.

A pulley is a simple machine that uses a wheel, rope, or chain to lift heavy objects. It reduces the effort needed to lift a load by changing the direction of the force. Pulleys are commonly used in wells to draw water or in cranes to lift heavy materials.

4. Define wedge.

A wedge is a simple machine that has a sharp edge. It is used to split or cut objects, or to hold them in place. Examples of wedges are knives, axes, and nails.

G. Long Answer Questions

1. What is a simple machine? Name some simple machines and draw diagrams too.

A simple machine is a basic tool that makes our work easier by using force more effectively. It helps in lifting, cutting, or moving objects with less effort. Simple machines have few or no moving parts.

Some examples of simple machines are:

• Lever: A rigid bar that pivots around a fulcrum.
• Pulley: A wheel and rope system used for lifting.
• Inclined Plane: A flat surface that slopes to reduce effort in lifting.
• Wedge: A sharp tool for cutting or splitting.
• Wheel and Axle: A wheel attached to a rod for easier movement.
• Screw: An inclined plane wrapped around a cylinder for fastening.

2. What is a pulley? Explain different types of pulleys with examples.

A pulley is a simple machine that uses a wheel, rope, or chain to lift, lower, or move heavy objects. It reduces the effort needed by changing the direction of the applied force.

Types of Pulleys:

1. Fixed Pulley:
   1. The pulley is fixed in one position.
   1. It only changes the direction of the force.
   1. Example: A flagpole pulley.
2. Movable Pulley:
   1. The pulley moves along with the load.
   1. It reduces the amount of effort needed.
   1. Example: Pulley used in construction sites to lift heavy materials.
3. Compound Pulley:
   1. A combination of fixed and movable pulleys.
   1. It reduces the effort significantly.
   1. Example: Crane systems used to lift heavy equipment.

Pulleys are widely used in daily life, from lifting water from wells to operating elevators.