Multiple Choice Questions.............................
Question 1: In given figure, two boys A and B are shown applying force on a block. If the block moves towards the right, which one of the following statements is correct?
(a) The magnitude of force applied by A is greater than that of B.
(b) The magnitude of force applied by A is smaller than that of B.
(c) The net force on the block is towards A.
(d) The magnitude of force applied by A is equal to that of B.
Solution 1: (a) Magnitude of force applied by A is greater than that of B.
The magnitude of force exerted by A is greater than that of B as a result of the block shifts towards right i.e. towards B.
Question 2: In the circuit shown in below figure, when the circuit is completed, the hammer strikes the gong. Which of the following force is responsible for the movement of the hammer?
(a) gravitational force alone
(b) electrostatic force alone
(c) magnetic force alone
(d) frictional force alone
Solution 2: (c) magnetic force alone
As electric current passes through the coil, it acts as an electromagnet, producing magnetic energy. As a result, the only solution is magnetic energy.
Question 3: During dry weather, while combing hair, sometimes we experience hair flying apart. The force responsible for this is
(a) force of gravity.
(b) electrostatic force.
(c) the force of friction.
(d) magnetic force.
Solution 3: (b) electrostatic force.
Electrostatic force causes the comb and hair to become oppositely charged while combing the hair.
Question 4: Below given figure shows a container filled with water. Which of the following statements is correct about the pressure of water?
(a) The pressure at A > Pressure at B > Pressure at C.
(b) The pressure at A = Pressure at B = Pressure at C.
(c) The pressure at A < Pressure at B > Pressure at C.
(d) The pressure at A < Pressure at B.
Solution 4: (d) Pressure at A < Pressure at B
Once the water level rises, so does the depth.
Question 5: Two objects repel each other. This repulsion could be due to
(a) frictional force only
(b) electrostatic force only
(c) magnetic force only
(d) either a magnetic or an electrostatic force
Solution 5: (d) either a magnetic or an electrostatic force
When there is a repulsive force between two objects, it may be due to an electrostatic or magnetic force.
Question 6: Which one of the following forces is a contact force?
(a) force of gravity
(b) force of friction
(c) magnetic force
(d) electrostatic force
Solution 6: (b) force of friction
Only when the bodies are in touch does the force of attraction work.
Question 7: A water tank has four taps fixed at points A, B, C, D as shown given figure. The water will flow out at the same pressure from taps at
(a) B and C
(b) A and B
(c) C and D
(d) A and C
Solution 7: (a) B and C
Since B and C are at the same elevation, their pressures would be the same.
Question 8: A brick is kept in three different ways on a table as shown in Fig. 11.5. The pressure exerted by the brick on the table will be
(a) maximum in position A-C
(b) maximum in position B
(c) maximum in position
(d) equal in all cases.
Solution 8: (a) maximum in position A-C
Since the contact area is limited, pressure will be highest in A.
Very Short Answer Questions.........................
Question 9: A ball of dough is rolled into a flat chapatti. Name the force exerted to change the shape of the dough.
Solution 9: Muscular Force
Question 10: Where do we apply a force while walking?
Solution 10: We exert force on the ground while walking.
Question 11: A girl is pushing a box towards the east direction. In which direction should her friend push the box so that it moves faster in the same direction?
Solution 11: In the direction of east
Question 12: In the circuit shown in figure, when the key is closed, the compass needle placed in the matchbox deflects. Name the force which causes this deflection.
Solution 12: Magnetic force
Question 13: During dry weather, clothes made of synthetic fibre often stick to the skin. Which type of force is responsible for this phenomenon?
Solution 13: Electrostatic force
Question 14: While sieving grains, small pieces fall down. Which force pulls them down?
Solution 14: Force of gravity
Question 15: Does the force of gravity act on dust particles?
Solution 15: Yes, on dust particles force of gravity acts upon.
Question 16: A gas-filled balloon moves up. Is the upward force acting on it larger or smaller than the force of gravity?
Solution 16: The upward force is greater than the gravitational force.
Question 17: Does the force of gravitation exist between two astronauts in space?
Solution 17: Yes, between two astronauts in space, there is a gravitational force.
Short Answer Questions..........................
Question 18: A chapati maker is a machine which converts balls of dough into chapati. What effect of force comes into play in this process?
Solution 18: To make chapati, apply pressure to the dough.
Question 19: Below figure shows a man with a parachute. Name the force which is responsible for his downward motion. Will he come down with the same speed without the parachute?
Solution 19: His downward motion is due to the force of gravity. His speed will be faster if he lands without a parachute.
Question 20: Two persons are applying forces on two opposite sides of a moving cart. The cart still moves with the same speed in the same direction. What do you infer about the magnitudes and direction of the forces applied?
Solution 20: Since the applied force is of equal magnitude in the opposite direction, the cart travels in the same direction at the same speed.
Question 21: Two thermocol balls held close to each other move away from each other. When they are released, name the force which might be responsible for this phenomenon. Explain.
Solution 21: Because of electrostatic force, two Thermocol balls placed close together move away from each other. Due to repulsion between similar charges, the balls with similar charges pass away.
Question 22: Fruits detached from a tree fall down due to force of gravity. We know that a force arises due to the interaction between two objects. Name the objects interacting in this case.
Solution 22: Fruits detached from a tree fall down due to force of gravity. Gravitational force arises due to the interaction between two objects. The objects interacting in this case are Earth and fruits.
Question 23: A man is pushing a cart down a slope. Suddenly the cart starts moving faster and he wants to slow it down. What should he do?
Solution 23: A man is pushing a cart down a slope. Suddenly the cart starts moving faster and he wants to slow it down. In this situation he must exert a force to pull the cart up to the slope.
Question 24: Below figure shows a car sticking to an electromagnet. Name the forces acting on the car? Which one of them is larger?
Solution 24: The car is affected by magnetic force (in the upward direction) and gravity or the weight of the car (in the downward direction). The magnetic force is stronger than the gravitational force.
Long Answer Questions..........................
Question 25: An archer shoots an arrow in the air horizontally. However, after moving some distance, the arrow falls to the ground. Name the initial force that sets the arrow in motion. Explain why the arrow ultimately falls down.
Solution 25: The string is stretched by Archer using muscular energy. The arrow's form would change as a result of this. When the string is released, the arrow returns to its original location, providing the initial force required to start the motion. For a period of time, due to gravitational pull, it descends.
Question 26: It is difficult to cut cloth using a pair of scissors with blunt blades. Explain.
Solution 26: The blunt blade has a greater surface area than blades with a shard tip. As a result, the blunt blade causes low pressure, making cutting the fabric difficult. Sharp blades have a much smaller surface area, which increases the pressure caused. This makes cutting fabric with sharp blades simpler.
Question 27: Two rods of the same weight and equal length have different thickness. They are held vertically on the surface of sand as shown in given figure. Which one of them will sink move? Why?
Solution 27: Rod B has a smaller contact field. As a consequence, the rod's weight (Force) produces more strain. The same force causes less pressure in the case of the rod.
Question 28: Two women are of the same weight. One wears sandals with pointed heels while the other wears sandals with flat soles. Which one would feel more comfortable while walking on a sandy beach? Give reasons for your answer.
Solution 28: Women are the same height and walk with the same amount of weight. Women wearing flat-heeled sandals, on the other hand, would feel more relaxed walking on a sandy beach. This is because flat soles have a greater surface area than pointed heel sandals. In addition, the pressure exerted by pointed heels would be greater than that exerted by flat-soled sandals. This pressure can cause pointed-toe sandals to sink in the sand, making it difficult to walk on the sand.
Question 29: It is much easier to burst an inflated balloon with a needle than by a finger. Explain.
Solution 29: Since the needle has a wider contact area than the finger, it can put more pressure on an inflated balloon. This added pressure quickly pierces the surface of the balloon, causing it to burst.
Question 30: Observe the vessels A, B, C and D shown in figure carefully.
The volume of water taken in each vessel is as shown. Arrange them in the order of decreasing pressure at the base of each vessel. Explain.
Solution 30: D, B, A, C is the order of decreasing pressure at the base of each vessel.
Since the pressure of a liquid column is determined by its height rather than the volume of the liquid.