Class 8 General Science Notes: - Unit-8: Force and Pressure : Solved Exercise (Long Questions and Answers)

(National Book Foundation - New Book/New Syllabus Based on National Curriculum Pakistan 2023-2024 and Onwards)

(Class 8 General Science Notes for 8th Centralized Exam 2023-2024 and onward, FDE, Islamabad)

C. Long Questions

Q1. What is the net force? How does it affect the motion of an object?

Ans:

The net force is the combined effect of all the forces acting on an object. The net force tells us whether the forces on the object are balanced or unbalanced.

a) Balanced Forces: - When the forces on an object produce a net force of zero (0) N, the forces are balanced forces. For example, a light bulb hanging from the ceiling does not move due to balanced forces.

b) Unbalanced Forces: - When the net force on an object is not zero (0) N, the forces on the object are unbalanced. For example, when the golf ball is hit, it receives an unbalanced force.

Q2. How is pressure related to force and area?

Ans:

Pressure: - The force acting on a unit area of a surface is called pressure

Pressure = Force / Area

The smaller the area, the larger the pressure on a surface for the same force larger the area smaller will be the pressure.

Q3. What is buoyancy? What determines the object to sink or float?

Buoyancy: - Buoyancy or upthrust, is an upward force exerted by a fluid that opposes the weight of an immersed object.

Buoyant force arises because pressure increases with depth in a fluid.

If the buoyant force is greater than the object’s weight, the object will rise to the surface and float.
If the buoyant force is less than the object’s weight, the object will sink.
If the buoyant force equals the object’s weight the object will remain suspended at that depth.

Unit-8: Force and Pressure: Solved Short Questions and Answers

Class 8 General Science Notes

Source: General Science Book (National Book Foundation, Pakistan)

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