NEET Physics: Motion in One Dimension questions with solutions

Q1. A ball thrown in the air reaches a height of \( 10 \mathrm{m} \) and drops down to the ground. Find the time taken by the ball to complete this entire journey.

1. \( 2.78 \mathrm{sec} \)
2. 3.40 sec
3. 1.43 sec
4. 2.86 sec

Answer: 2.86 sec

At the top of the motion, the velocity becomes zero, so the initial speed is determined by the maximum height using kinematics. Once that speed is known, the total time is twice the time to rise to the peak, giving 2.86 s.

Q2. The graphs below show that position versus time for three different cars: 1,2 and \( 3 . \) Rank these cars according to the magnitudes of their velocities, greatest first

1. 1,2,3
2. 3,2,1
3. 2,1,3
4. 2,3,1 E. All tie

Answer: 3,2,1

For a position versus time graph, the magnitude of velocity is the absolute value of the slope. The line for car 3 is steepest, car 2 is next, and car 1 is least steep, so the ranking is 3, 2, 1.

Q3. Assertion Two balls of different masses are thrown vertically upward with same speed. They will pass through their point of projection in the downward direction with the same speed. Reason The maximum height and downward velocity attained at the point of projection are independent of the mass of the ball.

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
3. Assertion is correct but Reason is incorrect
4. Both Assertion and Reason are incorrect

Answer: Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

For vertical motion under gravity (neglecting air resistance), the ball’s kinetic energy converts to potential energy and back, so the speed at the original height is the same as the launch speed. Since mass cancels in the energy equation, both balls return with the same downward speed, making the assertion true and the reason the correct explanation.