NEET (UG)

Practice Test 1 — Laws of Motion

12 questions • 18 minutes • auto-graded with full solutions

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Section A — MCQ (Single Correct)

Question 1

A net force of $12\ \text{N}$ acts on a $3\ \text{kg}$ body. Its acceleration is:

Solution: $a = F/m = 12/3 = 4\ \text{m/s}^2$.

Question 2

The impulse on a body equals its change in:

Solution: Impulse = change in momentum.

Question 3

A $0.5\ \text{kg}$ ball hits a wall at $6\ \text{m/s}$ and rebounds at $6\ \text{m/s}$. The magnitude of change in momentum is:

Solution: $\Delta p = m(v-(-v)) = 0.5\times12 = 6\ \text{kg}\cdot\text{m/s}$.

Question 4

A block on a flat floor needs more force to start than to keep moving because:

Solution: Static friction (max) exceeds kinetic friction.

Question 5

The centripetal force on a $1\ \text{kg}$ body moving at $2\ \text{m/s}$ in a circle of radius $0.5\ \text{m}$ is:

Solution: $F = mv^2/r = 1\times4/0.5 = 8\ \text{N}$.

Question 6

A man jumps from a boat to the shore. The boat moves backward because of conservation of:

Solution: Total momentum stays zero, so the boat recoils.

Question 7

On a frictionless incline of $30^{\circ}$, the acceleration of a sliding block is ($g = 10$):

Solution: $a = g\sin\theta = 10\times0.5 = 5\ \text{m/s}^2$.

Question 8

The minimum speed at the top of a vertical circle of radius $r$ is:

Solution: At the top, gravity provides the centripetal force: $v_{top} = \sqrt{gr}$.

Section B — Assertion & Reason

Question 9

A: Action and reaction forces do not cancel each other.
R: They act on two different bodies.

Solution: Because they act on different bodies, they cannot cancel — R explains A.

Question 10

A: A cricketer pulls the hands back while catching a fast ball.
R: Increasing the time of impact reduces the force for the same change in momentum.

Solution: The impulse–momentum theorem explains the technique — R explains A.

Question 11

A: In an inertial frame, centrifugal force is a real force acting on a body in circular motion.
R: In an inertial frame, the net force in uniform circular motion is the centripetal force directed toward the centre.

Solution: Centrifugal force is a pseudo-force, not real in an inertial frame, so A is false. The real net force is the inward (centripetal) force, so R is true.

Question 12

A: Friction is independent of the apparent area of contact.
R: Friction depends only on the normal reaction and the nature of the surfaces.

Solution: Friction = μN, set by N and the surfaces, not the apparent area — R explains A.