CBSE Class 11 Physics Motion in a Plane Worksheet Set A

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. The velocity of projection of oblique projectile is (6î + 8ĵ) 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 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. 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. In a two dimensional motion, instantaneous speed v₀ is a positive constant. Then, which of the following are necessarily true?
(a) The average velocity is not zero at any time
(b) Average acceleration must always vanish
(c) Displacements in equal time intervals are equal
(d) Equal path lengths are traversed in equal intervals

Answer: D

Question. From a 10 m high building a stone A is dropped, and simultaneously another identical stone B is thrown horizontally with an initial speed of 5 ms^–1. Which one of the following statements is true?
(a) It is not possible to calculate which one of the two stones will reach the ground first
(b) Both the stones (A and B) will reach the ground simultaneously
(c) A stone reaches the ground earlier than B
(d) B stone reaches the ground earlier than A

Answer: B

Question. If |A̅ x B̅| = √3A̅B̅ then the value of |A̅ + B̅| is
(a) (A² + B² √3AB)^½
(b) (A² + B² + AB)^½
(c) (A² + B² + AB/√3)^½
(d) A + B

Answer: B

Question. If a vector 2î + 3ĵ + 8k̂is perpendicular to the vector 4ĵ - 4î + αk̂, then the value of α is 
(a) 1/2
(b) –1/2
(c) 1
(d) –1

Answer: B

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. The equation of trajectory of projectile is given by y = x/√3 - gx2/20 , where x and y are in metre.
The maximum range of the projectile is
(a) 8/3 m
(b) 4/3 m
(c) 3/4 m
(d) 3/8 m

Answer: B

Question. Figure shows the orientation of two vectors u and v in the xy-plane. (3)
If u = aî + bĵ and v = pî + qĵ
Which of the following is correct?
(a) a and p are positive while b and q are negative
(b) a, p and b are positive while q is negative
(c) a, q and b are positive while p is negative
(d) a, b, p and q are all positive

Answer: B

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 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. 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. Vectors A̅.B̅ and C̅ are such that A̅.B̅ = 0 and A̅.C̅ = 0. 
Then the vector parallel to A̅ is
(a) B̅ and C̅
(b) A̅ x B̅
(c) B̅ + C̅
(d) B̅ x C̅

Answer: D

Question. A particle is moving such that its position coordinate (x, y) are
(2m, 3m) at time t = 0
(6m, 7m) at time t = 2 s and
(13m, 14m) at time t = 5s.
Average velocity vector (V̅_av) from t = 0 to t = 5s is :
(a) 1/5 (13î + 14ĵ)
(b) 7/3 (î+ ĵ)
(c) 2(î+ ĵ)
(d) 11/5(î+ ĵ)

Answer: D

Question. The angle between A = î + ĵ and B = î - ĵ is
(a) 45°
(b) 90°
(c) – 45°
(d) 180°

Answer: B

Question. If vectors A̅ = cosωtî + sinωtĵ and B̅ = cos ωt/2 î + sin ωt/2 ĵ are functions of time, then the value of t at which they are orthogonal to each other is :
(a) t = π/2ω
(b) t = π/ω
(c) t = 0
(d) t = π/4ω

Answer: B

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 v m/sec²
(b) 40 m/sec²
(c) 640 π m/sec²
(d) 160 π m/sec²

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. 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. 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. 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) 0h

Answer: A

Directions for : Each question contains
STATEMENT-1 and STATEMENT-2. Choose the correct answer 
(a) Statement -1 is false, Statement-2 is true
(b) Statement -1 is true, Statement-2 is true; Statement -2 is a correct explanation for Statement-1
(c) Statement -1 is true, Statement-2 is true; Statement -2 is not a correct explanation for Statement-1
(d) Statement -1 is true, Statement-2 is false

Question. Statement-1: Two stones are simultaneously projected from level ground from same point with same speeds but different angles with horizontal. Both stones move in same vertical plane. Then the two stones may collide in mid air.
Statement-2 : For two stones projected simultaneously from same point with same speed at different angles with horizontal, their trajectories may intersect at some point.

Answer: D

Question. Statement-1 : K.E. of a moving body given by as2 where s is the distance travelled in a circular path refers to a variable acceleration.
Statement-2 : Acceleration varies with direction only in this case of circular motion.

Answer: D

Question. Statement -1 : 

Statement -2 : Cross product of vectors is commutative.

Answer: D

Question. Statement-1 : Centripetal and centrifugal forces cancel eachother.
Statement-2 : This is because they are always equal and opposite.

Answer: A

Question. Statement -1 : If dot product and cross product of A̅ and B̅ are zero, it implies that one of the vector A̅ and B̅ must be a null vector.
Statement -2 : Null vector is a vector with zero magnitude.

Answer: C