Q1: What is friction? (a) A force that makes objects move faster (b) A force that stops or slows down movement (c) A force that lifts objects upwards (d) A force that only works in water
Solution:
Ans: (b) Explanation: Friction is a force that stops or slows down the movement of an object when two surfaces touch or rub against each other.
Q2: Why is it harder to push a box on a carpet than on a wooden floor? (a) The carpet is heavier than the wooden floor (b) The carpet has more friction because it is a rough surface (c) The wooden floor is slippery like ice (d) The box becomes lighter on wooden floor
Solution:
Ans: (b) Explanation: Rough surfaces like carpets create more friction than smooth surfaces like wooden floors, making it harder to push objects on carpets.
Q3: How does friction help us when we walk? (a) It makes our shoes look nice (b) It provides grip between our feet and the ground (c) It makes us walk faster (d) It helps us jump higher
Solution:
Ans: (b) Explanation: Friction helps us walk by providing grip between our feet and the ground, which prevents us from slipping while walking.
Q4: What happens when we rub our hands together quickly? (a) Our hands become cold (b) Our hands produce heat due to friction (c) Our hands become wet (d) Our hands become sticky
Solution:
Ans: (b) Explanation: Rubbing hands together quickly produces heat due to friction between our palms, which makes our hands feel warmer.
Q5: How can we reduce friction on a carrom board? (a) By making the board wet (b) By sprinkling powder on it (c) By making it rough (d) By pressing harder on the striker
Solution:
Ans: (b) Explanation: Sprinkling powder on a carrom board reduces friction between the board and pieces, making the striker and coins move easily.
Fill in the Blanks
Q1: Friction acts in the _____ direction to the movement of an object.
Solution:
Ans: opposite
Q2: An ice cube slides more easily than a coin because liquids have _____ friction.
Solution:
Ans: less
Q3: Substances like oil or grease that reduce friction are called _____.
Solution:
Ans: lubricants
Q4: _____ objects experience more friction than lighter ones.
Solution:
Ans: Heavy
Q5: Friction between a pencil tip and paper allows us to _____.
Solution:
Ans: write
True or False
Q1: Friction only occurs in solids.
Solution:
Ans: False Explanation: Friction occurs in solids, liquids, and gases, but solids have more friction than liquids.
Q2: Smooth surfaces create more friction than rough surfaces.
Solution:
Ans: False Explanation: Rough surfaces create more friction than smooth surfaces, making it harder to move objects on rough surfaces.
Q3: Friction helps bicycles and vehicles to move or stop.
Solution:
Ans: True Explanation: Friction between tires and the ground allows bicycles and vehicles to move or stop properly.
Q4: Friction can be completely removed by using lubricants.
Solution:
Ans: False Explanation: Friction cannot be completely removed but can be reduced by using lubricants like oil, grease, or powder.
Q5: Wheels and rollers reduce friction to make movement easier.
Solution:
Ans: True Explanation: Wheels and rollers on items like luggage bags reduce friction, making it easier to move heavy objects.
Match the Following
Column A
Column B
1. Rubbing a matchstick against a rough surface
A. Reduces friction on a carrom board
2. Oiling door hinges
B. Increases friction for better grip
3. Sprinkling powder
C. Creates friction that lights the matchstick
4. Grooved shoe soles
D. Stops squeaking and makes movement smooth
5. Friction in brakes
E. Helps a car slow down or stop
Solution:
Ans:
1 - C: Rubbing a matchstick against a rough surface creates friction, which produces heat and lights the matchstick.
2 - D: Oiling door hinges reduces friction, which stops the squeaking sound and makes the hinges move smoothly.
3 - A: Sprinkling powder on a carrom board reduces friction, making the striker and coins move easily across the board.
4 - B: Grooved shoe soles increase friction with the ground, providing better grip and preventing slipping while walking.
5 - E: Friction in brakes helps a car slow down or stop when the driver applies the brakes.
Short Answer Questions
Q1: Why is walking on a wet floor harder than on a dry floor?
Solution:
Ans: Walking on a wet floor is harder than on a dry floor because water reduces the friction between our feet and the floor surface. This lack of friction makes it difficult to maintain grip, which can cause us to slip and lose balance. Friction provides the necessary grip needed for stable walking.
Q2: How does friction help us hold objects?
Solution:
Ans: Friction gives us the grip needed to hold objects firmly in our hands. When we hold items like books or water bottles, friction between our skin and the object's surface prevents them from slipping. Without friction, objects would easily slide out of our hands, making it impossible to carry or use them properly.
Q3: Explain how friction produces sound with an example.
Solution:
Ans: Friction produces sound when two surfaces rub against each other and vibrate. A good example is a violin, where friction between the bow and the violin string creates vibrations that produce musical sound. The rubbing action causes the string to vibrate, and these vibrations travel through the air as sound waves we can hear.
Q4: What are lubricants and how do they work?
Solution:
Ans: Lubricants are substances like oil, grease, or powder that make surfaces smoother and reduce friction between them. They work by creating a thin layer between two surfaces that rub against each other. This layer makes movement easier and prevents wear and tear. For example, oiling a bicycle chain reduces friction and helps it move smoothly.
Q5: How does friction cause wear and tear in machines?
Solution:
Ans: Friction causes wear and tear in machines when parts rub against each other continuously during operation. This rubbing action gradually damages the surfaces of machine parts, making them rough or worn out. Over time, this damage can reduce the machine's efficiency and may cause it to stop working properly, requiring repairs or replacement of parts.
The document Worksheet with Solutions: Friction as a Force is a part of the Class 4 Course Science Class 4 ICSE.
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