4. Answer the following questions in 60-80 words:
(8 marks)
a) State two advantages and two disadvantages of friction.
b) (i) Mohan runs a juice shop and his sugarcane crushing machine makes a loud noise.
Explain the cause and suggest a solution to this problem.
(ii) Anand and Ravi are cycling on a concrete road. Anand's bicycle has new tyres
while Ravi's has old ones. Who is more likely to skid if begins to rain? Why?
Answers
Answer:
a). Advantages of friction:
1. Friction enables us to walk freely.
2. It helps to support ladder against wall.
3. It becomes possible to transfer one form of energy to another.
4. Objects can be piled up without slipping.
5. Breaks of vehicles work due to friction.
Disadvantages of friction:
1.It always resists the motion, so extra energy is required to overcome it.
2.It causes wear and tear of machines.
3.It decreases the life expectancy of moving parts of vehicles.
4.Since friction is very useful in some cases while harmful in some cases, friction is called a necessary evil.
b).I). Mohan's sugarcane crushing machine makes a loud noise bcz rust has attacked the metal from which the machine is made from. ... This layer of brownish dust is called rust and the process is called rusting. For stopping this rusting mohan should galvanise his sugarcane crushing machine.
ii). because Ravi cycle is old and his tyre is old his bicycle tyre it more slippery and easy to run in rain.