CBSE Class 11 Physics Motion in a Plane MCQs Set C

Question. The velocity of projection of oblique projectile is (6 + 8j) ms^-1. The horizontal range of the projectile is
(a) 4.9 m
(b) 9.6 m
(c) 19.6 m
(d) 14 m
Answer: b

Question. A body is thrown horizontally with a velocity √2gh from the top of a tower of height h. It strikes the level ground through the foot of the tower at a distance x from the tower. The value of x is
(a) gh
(b) gh/2
(c) 2h
(d) 2gh/3
Answer: c

Question. A bullet is fired with a speed of 1500 m/s in order to hit a target 100 m away. If g = 10 m/s². The gun should be aimed
(a) 15 cm above the target
(b) 10 cm above the target
(c) 2.2 cm above the target
(d) directly towards the target
Answer: c

 Question. The position vector of a particle R^→ as a function of time is given by: R^→ = 4sin(2πt)ˆi + 4cos(2πt)ˆj Where R is in meter, t in seconds and ˆi and ˆj denote unit vectors along x-and y-directions, respectively. Which one of the following statements is wrong for the motion of particle?
(a) Magnitude of acceleration vector is v²/R , where v is the velocity of particle
(b) Magnitude of the velocity of particle is 8 meter/second
(c) path of the particle is a circle of radius 4 meter.
(d) Acceleration vector is along – R^→
Answer: b

Question. A particle moves so that its position vector is given by r^→ = cosϖtxˆ + sinϖtyˆ . Where w is a constant. Which of the following is true ?
(a) Velocity and acceleration both are perpendicular to r^→
(b) Velocity and acceleration both are parallel to r^→
(c) Velocity is perpendicular to r^→ and acceleration is directed towards the origin
(d) Velocity is perpendicular to r^→ and acceleration is directed away from the origin
Answer: c

Question. If the magnitude of sum of two vectors is equal to the magnitude of difference of the two vectors, the angle between these vectors is :
(a) 0°
(b) 90°
(c) 45°
(d) 180°
Answer: b

Question. A person sitting in the rear end of the compartment throws a ball towards the front end. The ball follows a parabolic path. The train is moving with velocity of 20 m/s. A person standing outside on the ground also observes the ball. How will the maximum heights (y_m) attained and the ranges (R) seen by the thrower and the outside observer compare with each other?
(a) Same y_m different R
(b) Same y_m and R
(c) Different y_m same R
(d) Different y_m and R
Answer: a

Question. The position vector of a particle is r^→ = (a cos ϖt) i + (a sin ϖt)j The velocity of the particle is
(a) directed towards the origin
(b) directed away from the origin
(c) parallel to the position vector
(d) perpendicular to the position vector
Answer: d

Question. A body of 3kg. moves in X-Y plane under the action of force given by 4ti^ˆ + 6tj . Assuming that the body is at rest at time t = 0, the velocity of body at t = 3 sec is
(a) 6 i^ˆ + 9j^ˆ
(b) 6 i^ˆ + 18j^ˆ
(c) 12 i^ˆ + 18j^ˆ
(d) 68 i^ˆ + 12j^ˆ
Answer: a

Question. The horizontal range of a projectile fired at an angle of 15° is 50 m. If it is fired with the same speed at an angle of 45°, its range will be
(a) 60 m
(b) 71 m
(c) 100 m
(d) 141 m
Answer: c

Question. A ship A is moving Westwards with a speed of 10 km h^–1 and a ship B 100 km South of A, is moving Northwards with a speed of 10 km h^–1. The time after which the distance between them becomes shortest, is :
(a) 5 h
(b) 5√2 h
(c) 10√2 h
(d) 0√h
Answer: a

Question. The vector sum of two forces is perpendicular to their vector differences. In that case, the forces
(a) cannot be predicted
(b) are equal to each other
(c) are equal to each other in magnitude
(d) are not equal to each other in magnitude
Answer: c

Question. The component of a vector r along X-axis will have maximum value if
(a) r is along positive Y-axis
(b) r is along positive X-axis
(c) r makes an angle of 45° with the X-axis
(d) r is along negative Y-axis
Answer: b

Question. The x and y coordinates of the particle at any time are x = 5t – 2t² and y = 10t respectively, where x and y are in meters and t in seconds. The acceleration of the particle at t = 2s is
(a) 5 m/s²
(b) –4 m/s²
(c) –8 m/s²
(d) 0
Answer: b

Question. A ball whose kinetic energy is E is thrown at an angle of 45º with horizontal. Its kinetic energy at highest point of flight will be
(a) E
(b) E/2
(c) E/√2
(d) O
Answer: b

Question. A cricket ball is hit with a velocity 25 ms^-1 , 60° above the horizontal. How far above the ground, ball passes over a fielder 50 m from the bat (consider the ball is struck very close to the ground)? Take √3 =1.7 and g = 10 ms^–2
(a) 6.8 m
(b) 7 m
(c) 5 m
(d) 10 m
Answer: c

Question. A body is thrown with a velocity of 9.8 ms^–1 making an angle of 30º with the horizontal. It will hit the ground after a time
(a) 3.0 s
(b) 2.0 s
(c) 1.5 s
(d) 1 s
Answer: d

Question. A projectile is moving at 60 m/s at its highest point, where it breaks into two equal parts due to an internal explosion. One part moves vertically up at 50 m/s with respect to the ground. The other part will move at a speed of
(a) 110 m/s
(b) 120 m/s
(c) 130 m/s
(d) 10 61 m/ s
Answer: c

Question. A body is projected at an angle of 30º to the horizontal with speed 30 m/s. What is the angle with the horizontal after 1.5 seconds? Take g = 10 m/s².
(a) 0º
(b) 30º
(c) 60º
(d) 90º
Answer: a

Question. Two projectiles are fired from the same point with the same speed at angles of projection 60º and 30º respectively. Which one of the following is true?
(a) Their maximum height will be same
(b) Their range will be same
(c) Their landing velocity will be same
(d) Their time of flight will be same
Answer: b

Question. Two bullets are fired horizontally, simultaneously and with different velocities from the same place. Which bullet will hit the ground earlier ?
(a) It would depend upon the weights of the bullets.
(b) The slower one.
(c) The faster one.
(d) Both will reach simultaneously.
Answer: d

Question. A gun is aimed at a horizontal target. It takes 1/2s for the bullet to reach the target. The bullet hits the target x metre below the aim. Then, x is equal to
(a) (9.8/4)m
(b) (9.8/8)m
(c) 9.8 m
(d) 19.6 m.
Answer: b

Question. Which one of the following statements is true?
(a) A scalar quantity is the one that is conserved in a process
(b) A scalar quantity is the one that can never take negative values
(c) A scalar quantity is the one that does not vary from one point to another in space
(d) A scalar quantity has the same value for observers with different orientation of the axes
Answer: d

Question. Let C→ = A→ + B→
(a) | C^→ | is always greater than | A ^→|
(b) It is possible to have | C^→ |<| A^→ | and | C^→|<| B^→|
(c) C^→ is always equal to A^→+ B^→
(d) C^→ is never equal to A^→+ B^→
Answer: b

Question. A projectile is thrown in the upward direction making an angle of 60° with the horizontal direction with a velocity of 147 ms^–1. Then the time after which its inclination with the horizontal is 45°, is
(a) 15 s
(b) 10.98 s
(c) 5.49 s
(d) 2.745 s
Answer: c

Question. The resultant of two forces 3P and 2P is R. If the first force is doubled then the resultant is also doubled. The angle between the two forces is
(a) 60º
(b) 120º
(c) 70º
(d) 180º
Answer: b

Question. A person swims in a river aiming to reach exactly on the opposite point on the bank of a river. His speed of swimming is 0.5 m/s at an angle of 120º with the direction of flow of water. The speed of water is
(a) 1.0 m/s
(b) 0.5 m/s
(c) 0.25 m/s
(d) 0.43 m/s
Answer: c

Question. A cyclist moving at a speed of 20 m/s takes a turn, if he doubles his speed then chance of overturn
(a) is doubled
(b) is halved
(c) becomes four times
(d) becomes 1/4 times
Answer: d

Question. A person aims a gun at a bird from a point at a horizontal distance of 100 m. If the gun can impact a speed of 500 ms^– 1 to the bullet. At what height above the bird must he aim his gun in order to hit it? (g = 10 ms^–2)
(a) 10.4 cm
(b) 20.35 cm
(c) 50 cm
(d) 100 cms
Answer: b

Question. In a two dimensional motion, instantaneous speed v0 is a positive constant. Then, which of the following are necessarily true?
(a) The acceleration of the particle is zero
(b) The acceleration of the particle is bounded
(c) The acceleration of the particle is necessarily in the plane of motion
(d) The particle must be undergoing a uniform circular motion
Answer: c

 Question. A force of (3^ˆi + 4^ˆj) N acts on a body and displaces it by (3ˆi + 4ˆj) m. The work done by the force is
(a) 5 J
(b) 30 J
(c) 25 J
(d) 10 J
Answer: c

Question. A particle having a mass 0.5 kg is projected under gravity with a speed of 98 m/sec at an angle of 60º. The magnitude of the change in momentum (in N-sec) of the particle after 10 seconds is
(a) 0.5
(b) 49
(c) 98
(d) 490
Answer: b

Question. Consider the quantities, pressure, power, energy, impulse, gravitational potential, electrical charge, temperature, area. Out of these, the only vector quantities are :
(a) impulse, pressure and area
(b) impulse and area
(c) area and gravitational potential
(d) impulse and pressure
Answer: b

Question. A plane flying horizontally at a height of 1500 m with a velocity of 200 ms^–1 passes directly overhead on antiaircraft gun. Then the angle with the horizontal at which the gun should be fired from the shell with a muzzle velocity of 400 ms^–1 to hit the plane, is
(a) 90°
(b) 60°
(c) 30°
(d) 45°
Answer: b

Question. At what angle must the two forces (x + y) and (x – y) act so that the resultant may be √(X² + Y²) ?
(a) cos^-1[-(x² + y² ) / 2(x² – y² )]
(b) cos^-1[-2(x² – y² ) /(x2 + y² )]
(c) cos^-1[-(x² + y² ) /(x² – y²)]
(d) cos^-1[-(x² – y² ) /(x² + y² )]
Answer: a

Question. A particle moves along a circle of radius (20/π)m with constant tangential acceleration. It the velocity of particle is 80 m/sec at end of second revolution after motion has begun, the tangential acceleration is
(a) 40 π m/sec²
(b) 40 m/sec²
(c) 640 π m/sec²
(d) 160 π m/sec²
Answer: b

Question. The angle between A = i^ˆ + ^ˆj and B = i^ˆ – ^ˆj is
(a) 45°
(b) 90°
(c) – 45°
(d) 180°
Answer: b

Question. The component of vector a^→ = 2ˆi + 3ˆj along the vector i + j is
(a) 5/√2
(b) 10√2
(c) 5√2
(d) 5
Answer: a