Conceptual Questions Based on Class 11 Physics Projectile Motion

Here we are providing conceptual questions for Class 11 Physics Projectile Motion. Answers are also provided along with questions. So that students can read and understand the question. These questions are prepared by the subject experts. Students can read these conceptual questions based on Projectile Motion for better topic clarity and therefore will be able to score better marks in their exam.

Conceptual Questions Based on Class 11 Physics Projectile Motion

Conceptual questions based on class Projectile Motion is given below. Go through each and every question to understand the topic clearly.

Q.1. Can there be motion in two dimensions with an acceleration only in one dimension?

Solution. Yes, in a projectile motion the acceleration acts vertically downwards while the projectile follows a parabolic path.

Q.2. Is the maximum height attained by projectile is largest when its horizontal range is maximum?

Solution. No. Horizontal range is maximum when θ = 45° and maximum height attained by projectile is largest when θ = 90°.

Q.3. a stone is thrown vertically upwards and then it returns to the thrower. Is it a projectile?

Solution. it is not a projectile, because a projectile should have two component velocities in two mutually perpendicular directions, but in this case the body has velocity only in one direction while going up or coming downwards.

Q.4. Can the direction of velocity of a body change when the acceleration is constant ?

Solution. Yes, in projectile motion the direction of velocity changes from point to point, but its acceleration is always constant and acts vertically downwards.

Q.5. A projectile of mass m is fired with velocity v at an angle θ with the horizontal. What is the change in momentum as it rises to the highest point of the trajectory?

Solution. Horizontal component of velocity remains constant. The vertical component is v sin θ at the point of projection and zero at the highest point.

Magnitude of change in momentum

= m (v sin 0 – 0) = mv sin θ (in the vertical direction)

Q.6. Is the rocket in flight an example of projectile?

Solution. No, because it is propelled by combustion of fuel and does not move under the effect of gravity alone.

Q.7. Why does a projectile fired along the horizontal not follow a straight-line path?

Solution. Because the projectile fired horizontally is constantly acted upon by acceleration due to gravity acting vertically downwards.

Q.8. A body projected horizontally moves with the same horizontal velocity although it is under the action of force of gravity. Why?

Solution. The force of gravity acts in the vertically downward direction and has no effect on the horizontal component of velocity; and this makes the body to move with constant horizontal velocity.

Q.9. A projectile of mass m is thrown with velocity v from the ground at an angle of 45° with the horizontal. What is the magnitude of change in momentum between leaving and arriving back at the ground?

Solution. The vertical component of velocity at the point of projection is v sin θ and at the point of return is – v sin θ.

∴ Magnitude of change in momentum

= m (v sin θ + v sin θ) = 2 mv sin θ

= 2 mv sin 45° (in the vertical direction).

Q.10. A block slides down a smooth inclined plane when released from the top while another falls freely from the same point. Which one of them will strike the ground earlier?

Solution. Acceleration of the freely falling block is g while that of the block sliding down the smooth inclined plane is g sin 0. As g > g sin θ, so the block falling freely will reach the ground earlier.

Q.11. What is the angle between the direction of velocity and acceleration at the highest point of a projectile path?

Solution. 90°. At the highest point the vertical component of velocity becomes zero, the projectile has only a horizontal velocity while the acceleration due to gravity acts vertically downwards.

Q.12. At what point in its trajectory does a projectile have its (i) minimum speed (ii) maximum speed?

Solution. For a projectile given angular projection, the horizontal component of velocity remains constant throughout while the vertical component first decreases, becomes zero at the highest point and then increases again. Hence

(i) Projectile has minimum speed at the highest point of its trajectory. (ii) Projectile has maximum speed at the point of projection and at the point where it returns to the horizontal plane of projection.

Q.13. A stone dropped from the window of a stationary bus takes 5 seconds to reach the ground. In what time the stone will reach the ground when the bus is moving with (a) constant velocity of 80 kmh^-1 (b) constant acceleration of 2 kmh^-2 ?

Solution. (a) 5 seconds (b) 5 seconds. In both cases, initial vertical velocity is zero, downward acceleration is equal to ‘g’ and also vertical distance covered is same.

Q.14. A ball is thrown horizontally and at the same time another ball is dropped down from the top of a tower (i) Will both the balls reach the ground at the same time ? (ii) Will both strike the ground with the same velocity ?

Solution. (i) Yes, because the initial vertical velocity of both the balls is zero, and both will cover the same vertical distance under the same vertical acceleration g.

(ii) No, because on striking the ground although their vertical velocities will be same but horizontal velocities will be different. Hence their resultant velocities will be different.

Q.15. A bomb thrown as projectile explodes in mid-air. What is the path traced by the centre of mass of the fragments assuming the friction to be negligible?

Solution. The path traced by the centre of mass of the fragments is a parabola.

Q.16. A projectile is fired at an angle of 15° to the horizontal with the speed v. If another projectile is projected with the same speed, then at what angle with the horizontal it must be projected so as to have the same range?

Solution. For same R and v, the sum of the two angles of projection is 90°. As one angle is of 15°, other should be 90° – 15° = 75°.

Q.17. A bullet is dropped from a certain height and at the same time, another bullet is fired horizontally from the same height. Which one will hit the ground earlier and why?

Solution. Since the heights of both bullets from the ground is the same, so the time taken by both of them to reach the ground will be the same.

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Conceptual Questions Based on Class 11 Physics

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