Class 8 Science - Chapter 5 Practice Test

Force: A push or a pull upon an object resulting from the object's interaction with another object.
Effects of Force:
- Can change the state of motion (speed or direction) of an object (e.g., catching a ball).
- Can change the shape of an object (e.g., stretching a rubber band).

Contact Forces: Forces that act only when objects are physically touching.
- Muscular Force: Force exerted by muscles (e.g., lifting a bucket).
- Friction: Force that opposes motion between surfaces in contact (e.g., a ball rolling to a stop).
Non-Contact Forces: Forces that act from a distance without physical contact.
- Magnetic Force: Attraction or repulsion between magnets or magnetic materials.
- Electrostatic Force: Force exerted by a charged body on another charged or uncharged body (e.g., rubbed straw attracting paper).
- Gravitational Force: The force of attraction between all objects in the universe. Earth's gravity pulls objects down.

Pressure: Force acting on a unit area of a surface.
Formula: Pressure = Force / Area
Smaller area = Higher pressure (e.g., a sharp knife cuts better because the force is concentrated on a small area).
Atmospheric Pressure: The pressure exerted by the weight of air around us. It decreases as we go higher up.

Liquids and gases exert pressure on the walls of their container.
Pressure in a liquid increases with depth (e.g., water spurts out faster from a hole near the bottom of a bottle).

⚙️ Chapter 5 Revision Notes