Force and Pressure — Previous Year Questions (Class 8 Science)
Explore forces, motion, and pressure. Understand Newton's laws and how pressure affects different surfaces.
TL;DR: Explore forces, motion, and pressure. Understand Newton's laws and how pressure affects different surfaces.
Written & reviewed by the Syllab.in Academic Team (CBSE/NCERT subject experts) · Updated
Explore forces, motion, and pressure. Understand Newton's laws and how pressure affects different surfaces.
Force and Pressure — Previous Year Questions with Solutions
Q (2023, 3 marks): Define force and pressure. What is the relationship between them?
Answer: Force: A push or pull that can change the motion or shape of an object. SI unit: Newton (N).
Pressure: Force per unit area. Pressure = Force / Area. SI unit: Pascal (Pa) or N/m^2.
Relationship: Pressure is directly proportional to force and inversely proportional to area.
Higher force or smaller area results in higher pressure.
Q (2022, 3 marks): A man stands on the ground with both feet. Later, he stands on one foot. In which case is the pressure on the ground more? Why?
Answer: Standing on one foot produces more pressure.
Reason: Pressure = Force / Area
When standing on both feet: Force = mg, Area = 2A (both feet)
When standing on one foot: Force = mg, Area = A (one foot)
Since area decreases while force remains the same, pressure increases.
Pressure on one foot = 2 × (Pressure on both feet)
Q (2023, 3 marks): What is friction? Name three types of friction.
Answer: Friction: A force that opposes relative motion between two surfaces in contact.
Three types:
1. Static friction: Acts between surfaces at rest. Example: A book on a table.
2. Sliding friction: Acts when surfaces slide. Example: A hockey puck sliding on ice.
3. Rolling friction: Acts when objects roll. Example: A wheel rolling on ground.
Rolling friction is usually smallest.
Q (2022, 2 marks): Why do we need friction? Give two examples where friction is useful.
Answer: Friction is needed because:
1. Walking: Without friction between shoes and ground, we cannot walk.
2. Writing: Friction between pen and paper allows writing.
Other examples: Brakes in vehicles, holding objects, climbing.
Q (2023, 2 marks): A force of 100 N is applied on an area of 5 m^2. Calculate the pressure.
Answer: Given: Force = 100 N; Area = 5 m^2
Pressure = Force / Area
Pressure = 100 / 5 = 20 Pa (Pascal)
Q (2022, 3 marks): Why are sharp tools like knives more effective than blunt ones for cutting?
Answer: Sharp tools have a smaller surface area in contact with the material being cut.
Since Pressure = Force / Area, a smaller area produces higher pressure for the same force.
Higher pressure concentrates the force on a small area, making it easier to cut through the material.
A knife concentrates the force on its sharp edge, creating very high pressure.
Frequently Asked Questions
What is the SI unit of pressure?
The SI unit of pressure is Pascal (Pa), which is equal to 1 Newton per square meter (N/m^2). Other units include atmosphere (atm), bar, and psi (pounds per square inch).
Why do we feel more pressure under water when going deeper?
As we go deeper, the weight of water above us increases. This weight creates more pressure. Pressure underwater increases with depth because P = atmospheric pressure + (density × g × depth).
More Class 8 Science PYQs
- Chemical Reactions and Equations
- Light (Reflection and Refraction)
- Electricity
- Acids, Bases and Salts
- Metals and Non-metals
- Life Processes
🤖 Stuck on any of these? Ask Syllab's free AI Tutor to explain step by step →