Hard

Exploring Forces — Hard

15 questions 18 min PYQ-grade reasoning

Q1. Consider these statements about a polished marble floor just mopped: I. Water fills the tiny irregularities of the floor. II. Friction between shoe and floor increases sharply. III. Reduced friction is why we slip more easily. Which are correct?
- A. I and II only
- B. II and III only
- C. I and III only
- D. All three
Q2. Assertion (A): The weight of a 1 kg object changes from 10 N on the Earth to about 1.6 N on the Moon. Reason (R): The mass of the object also becomes one-sixth on the Moon.
- A. Both A and R are true, and R is the correct explanation of A.
- B. Both A and R are true, but R is NOT the correct explanation of A.
- C. A is true, R is false.
- D. A is false, R is true.
Q3. According to Archimedes' principle, an object will float in a liquid if
- A. The weight of the liquid displaced is greater than the weight of the object
- B. The weight of the liquid displaced equals the weight of the object
- C. The weight of the liquid displaced is much less than the weight of the object
- D. No liquid is displaced at all by the object
Q4. A book lies at rest on a table. Which of the following best describes the forces on the book?
- A. No force at all acts on the book
- B. Only gravity acts on the book
- C. Gravity acts downwards and the table pushes up with an equal force, balancing it
- D. Only friction from the table acts on the book
Q5. A balloon is rubbed with a woollen cloth. After rubbing: I. The balloon and the cloth carry charges of the same kind. II. The balloon and the cloth carry charges of opposite (unlike) kinds. III. The balloon and the cloth therefore attract each other. Which of the statements are correct?
- A. I and II only
- B. II and III only
- C. I and III only
- D. All three
Q6. A ball is thrown vertically upwards and returns to the ground. The forces acting on the ball during its upward journey, downward journey and at its highest point are
- A. Different in each phase — only acts during upward journey
- B. Gravity acts only when the ball is moving down
- C. Gravity acts downwards throughout — during upward motion, at the topmost point, and during downward motion
- D. No force acts at the topmost point because the ball is momentarily at rest
Q7. Three objects 1, 2 and 3 of the same size and shape but different materials are placed in water. They dip to different depths as in Fig. 5.17 (object 1 deepest, 3 just at the surface). If their weights are w1, w2 and w3, which is true?
- A. w1 = w2 = w3
- B. w1 > w2 > w3
- C. w2 > w3 > w1
- D. w3 > w1 > w2
Q8. A ball is released from a point P on an inclined plane and moves along a horizontal surface, coming to rest at point A (Fig. 5.16). To make the ball stop BEFORE point A when released from the same P, the best strategy is to
- A. Polish the horizontal surface to make it smoother
- B. Make the horizontal surface rougher so that friction increases
- C. Increase the height of P slightly
- D. Use a lighter ball of the same size
Q9. Consider the statement: 'A force is always required to change the speed of motion of an object.' This statement is
- A. False, because objects can speed up on their own
- B. True, because change in speed cannot occur without the action of a force
- C. False, because friction can also change the shape of an object
- D. True, but only when the object is initially at rest
Q10. On a spring balance scale (Fig. 5.13), the difference between two bigger marks 0 N and 01 N is 1 N, and there are 5 equal divisions between them. The smallest weight the scale can read is
- A. 0.5 N
- B. 0.2 N
- C. 1 N
- D. 0.1 N
Q11. Consider the following claim made by Rohan: 'There is no force between two charged objects placed at a small distance apart.' This claim is
- A. True, because the objects are not in contact
- B. True, only if both carry like charges
- C. False, because electrostatic force is a non-contact force that acts between them
- D. True, only if the air around them is dry
Q12. Statements about friction in fluids: I. Air exerts a frictional force on objects moving through it. II. Water exerts a frictional force on ships moving through it. III. Friction in fluids has no effect on the design of aeroplanes. Which are correct?
- A. I and II only
- B. II and III only
- C. I and III only
- D. All three
Q13. Assertion (A): An object dropped from a height takes a straight vertical path downwards before touching the ground. Reason (R): The gravitational force on the object acts in a vertical direction, pulling it towards the Earth.
- A. Both A and R are true, and R is the correct explanation of A.
- B. Both A and R are true, but R is NOT the correct explanation of A.
- C. A is true, R is false.
- D. A is false, R is true.
Q14. An empty closed bottle is pushed under water and released. It bounces back to the surface. The bounce-back proves that
- A. Water exerts a downward force on the bottle
- B. The bottle has lost its mass under water
- C. Water exerts an upward force (buoyant force) larger than the bottle's weight
- D. Gravity stops acting on the bottle inside water
Q15. Statements about contact forces: I. Pushing a table with the bare hand is a contact force. II. Pulling a bullock by a rope is also a contact force, through the rope. III. Earth pulling a falling apple is a contact force because air touches the apple. Which are correct?
- A. I and II only
- B. II and III only
- C. I and III only
- D. All three

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