Force and Pressure quiz

The SI unit of force is the:

Which of the following is a non-contact force?

Pressure is defined as:

The pressure exerted by a liquid in a container:

Two forces of 8 N and 5 N act on an object in opposite directions. The net force is:

The SI unit of pressure is the:

A charged balloon attracts small bits of paper because of:

School bags are given wide straps in order to:

The force that makes a ball thrown upwards fall back to the ground is:

The walls of a dam are made thicker at the bottom because:

Give two examples each of a push and a pull from your daily life. (2 marks)

Give one example each of a force changing (i) the speed (ii) the shape of an object. (2 marks)

What is muscular force? Name two animals that use muscular force to do work for us. (2 marks)

Why is it easier to cut vegetables with a sharp knife than with a blunt knife? (2 marks)

What is friction? In which direction does it act on a moving object? (2 marks)

Why does a balloon get inflated when air is blown into it? (2 marks)

Explain why a porter places a round piece of cloth on his head before carrying a heavy load. (2 marks)

What is gravity? Is it a contact or non-contact force? (2 marks)

Why does water come out faster from a hole near the bottom of a bottle than from a hole near the top? (2 marks)

Why do deep-sea divers wear special suits? (2 marks)

A block weighing 200 N has faces of areas 0.2 m^2, 0.5 m^2 and 0.8 m^2. Find the maximum and minimum pressure it can exert on the ground. (3 marks)

A force of 50 N is applied on a drawing pin whose tip has an area of 0.01 cm^2. Find the pressure at the tip in N/cm^2. What would the pressure be if the tip were blunt with an area of 0.5 cm^2? (3 marks)

An elephant weighing 40,000 N stands on four feet, each of area 0.1 m^2. Find the pressure it exerts on the ground. Compare it with the pressure exerted by a 500 N girl wearing heels of total area 0.001 m^2. (3 marks)

The atmospheric pressure is about 1,00,000 N/m^2. Find the force of the air on a square area of side 15 cm. What mass on Earth has a weight equal to this force? (Take the weight of 1 kg to be 10 N.) (3 marks)

In a tug of war, team P pulls with forces of 400 N, 350 N and 300 N from its three members, and team Q pulls with 380 N, 360 N and 340 N. Find the total force of each team, the net force and the direction in which the rope moves. (3 marks)

Read the passage and answer the questions. Rahul and his friends were pushing a car that had broken down. When Rahul pushed alone, the car did not move. When three friends pushed together in the same direction, it started moving slowly. Later, a truck coming from the opposite side pushed the car back. (i) Why did the car move only when the friends pushed together? (ii) What happens to the net force when forces act in the same direction and in opposite directions? (iii) Name two effects of force seen in this situation. (5 marks)

Read the passage and answer the questions. A student took a plastic bottle, made three holes at different heights in a vertical line, and filled it with water. Water came out from all the holes, but the stream from the lowest hole went the farthest. (i) What does this show about the pressure of water at different depths? (ii) What does it show about the walls of the bottle? (iii) Use this idea to explain why water tanks are placed on rooftops. (5 marks)

Read the passage and answer the questions. A tailor pressed a rubber sucker firmly on a smooth glass window to hang a decoration. The sucker stuck firmly and could not be pulled off easily. When a tiny hole was made in it, it fell off. (i) Why did the sucker stick to the glass? (ii) Why did it fall off when a hole was made? (iii) Name another everyday example that shows the effect of atmospheric pressure. (5 marks)

Read the passage and answer the questions. During a desert safari, tourists noticed that a camel walked easily on soft sand, while a jeep with narrow tyres got stuck. The driver lowered the air pressure in the tyres so that the tyres became wider at the bottom, and the jeep moved again. (i) Why could the camel walk easily on sand? (ii) Why did the jeep with narrow tyres sink into the sand? (iii) Explain how widening the tyres helped. (5 marks)

Read the passage and answer the questions. In a physics lab, Meena rubbed a plastic comb on her dry hair and brought it near small pieces of paper, which jumped up and stuck to the comb. She then brought a magnet near some iron pins, which also moved towards it without being touched. (i) Name the forces acting in both cases. (ii) Why are these called non-contact forces? (iii) Give one more example of a non-contact force. (5 marks)

Draw a labelled diagram of the activity using a plastic bottle with holes at different heights filled with water. Explain how it shows that liquids exert pressure on the walls of a container and that pressure increases with depth. Explain why the walls of dams are thicker at the bottom. (6 marks)

Define pressure and derive its unit. Draw diagrams of a brick placed on its largest face and on its smallest face on soft sand. A brick of weight 30 N measures 0.2 m by 0.1 m by 0.05 m; find the pressure in each position, and explain the difference. (6 marks)

Draw diagrams showing contact and non-contact forces: a hand pushing a box, friction acting on a rolling ball, a magnet attracting a pin and a charged comb attracting paper. Explain each type of force with examples. (6 marks)

Draw a labelled diagram of a column of air above the Earth's surface. Explain atmospheric pressure, calculate the force of the air on a 15 cm by 15 cm area (atmospheric pressure 1,00,000 N/m^2), and explain why we are not crushed by it. Describe the rubber sucker activity. (6 marks)

Using diagrams with arrows, show (i) two equal forces acting in opposite directions (ii) two forces acting in the same direction (iii) a force changing the direction of a moving ball. Explain the net force in each case, and describe how a force can change the speed, direction and shape of an object. (6 marks)