Friction quiz

Friction always acts:

Which of the following types of friction is the smallest?

A device used to measure the force acting on an object is a:

Friction can be reduced by:

Friction is caused by:

Ball bearings are used in machines to:

The friction exerted by fluids is called:

Which surface would give the greatest friction to a sliding brick?

When we rub our hands together, they become warm because:

Kabaddi players rub their hands with soil in order to:

Why is it difficult to walk on a smooth wet floor or on ice? (2 marks)

Why is static friction greater than sliding friction? (2 marks)

Why are the soles of shoes grooved? (2 marks)

Why are wheels used in vehicles and suitcases? (2 marks)

Why does a match light when it is struck on the side of the box? (2 marks)

Why do the soles of shoes and tyres of vehicles wear out with time? (2 marks)

Why should we not use oil or grease to reduce friction in the brakes of a bicycle? (2 marks)

Why is it easier to drag a bag on a smooth floor than on a rough carpet? (2 marks)

What would happen if there were no friction at all? Give two examples. (2 marks)

Why do aeroplanes and boats have streamlined shapes? (2 marks)

A spring balance shows 8 N just as a wooden block starts to slide, 6 N while it slides steadily, and 1.5 N when the block is placed on a toy car and pulled. Identify the static, sliding and rolling friction, and find how many times the sliding friction is greater than the rolling friction. (3 marks)

A man pushes a cupboard with a force of 250 N, but it does not move. What is the force of friction acting on it? He then pushes with 320 N and it just begins to move. What is the maximum static friction? (3 marks)

A cyclist pedals with a force that produces a forward push of 60 N, and the total friction and air resistance acting on the bicycle is 45 N. Find the net force and state whether the cyclist speeds up or slows down. What happens if the opposing forces become 60 N? (3 marks)

A trolley needs 200 N to be pulled on a rough road but only 150 N after its wheels are oiled. Find the reduction in force and the percentage reduction. (3 marks)

The reading of a spring balance pulling a matchbox along a table increases from 1 N to 2 N to 3 N as 1, 2 and 3 identical weights are placed on it. Describe the relationship between the weight on the box and friction, and predict the reading when 5 weights are placed on it. (3 marks)

Read the passage and answer the questions. Riya tied a string to a brick and pulled it with a spring balance on a smooth floor, then on a jute bag spread on the floor, and finally after placing the brick on three round pencils. She noted the reading each time the brick moved steadily. (i) On which surface was the reading the highest? Why? (ii) Why was the reading the lowest when pencils were placed under the brick? (iii) Name the type of friction in the last case. (5 marks)

Read the passage and answer the questions. The tyres of a car were worn out and had become smooth. During a rainy day, the car skidded when the driver applied the brakes. The mechanic advised the owner to replace the tyres with new ones having deep treads. (i) Why did the car skid? (ii) How do treads on tyres help on wet roads? (iii) Why do tyres wear out with use? (5 marks)

Read the passage and answer the questions. In a factory, the moving parts of machines become hot and noisy and wear out quickly. The engineer orders oiling of the moving parts and fitting ball bearings between the axles and the hubs of the wheels. (i) Why do the moving parts become hot? (ii) How does oiling reduce friction? (iii) How do ball bearings reduce friction? (5 marks)

Read the passage and answer the questions. A skydiver jumps from an aeroplane and falls faster and faster at first. After opening the parachute, the speed of fall decreases and he lands safely. (i) Name the force that slows down the skydiver after the parachute opens. (ii) Why does the parachute increase this force? (iii) On what factors does this force depend? (5 marks)

Read the passage and answer the questions. A gymnast applies a coarse white powder on her hands before holding the bars, while a carrom player sprinkles fine powder on the carrom board before the game. (i) Why does the gymnast use the powder? (ii) Why does the carrom player use the powder? (iii) Using these examples, explain why friction is called a necessary evil. (5 marks)

Draw a labelled diagram of the activity in which a brick is pulled on different surfaces using a spring balance. Explain what the readings show about the factors on which friction depends, and explain the cause of friction with a magnified diagram of the surfaces. (6 marks)

Draw diagrams showing (i) a box being pushed but not moving (ii) a box sliding on the floor (iii) a box placed on rollers. Explain static, sliding and rolling friction using these diagrams and arrange them in order of magnitude. (6 marks)

Draw a labelled diagram of ball bearings in a wheel. Describe four methods of reducing friction and four methods of increasing friction, giving one example of where each method is used. (6 marks)

Draw the streamlined shapes of a fish, a bird and an aeroplane. Explain fluid friction, the factors on which it depends, and how streamlining reduces it. Why are fish and birds naturally streamlined? (6 marks)

Draw labelled diagrams showing friction helping us (i) walk (ii) write with a pencil (iii) stop a bicycle with brakes. Explain the advantages and disadvantages of friction and justify the statement "friction is a necessary evil". (6 marks)