JEE Physics Quiz Rectilinear Motion MCQ

A hall has the dimensions 10 m × 10 m × 10 m. A fly starting at one corner ends up at a farthest corner. The magnitude of its displacement is:

1. 5√3 m
2. 10√3 m
3. 20√3 m
4. 30√3 m

A car travels from A to B at a speed of 20 km h^–1 and returns at a speed of 30 km h^–1. The average speed of the car for the whole journey is :

1. 5 km h^–1
2. 24 km h^–1
3. 25 km h^–1
4. 50 km h^–1

A person travelling on a straight line without changing direction moves with a uniform speed v₁ for half distance and next half distance he covers with uniform speed v₂. The average speed v is given by

1. v = 2v₁v₂/v₁ + v₂
2. v = √v₁v₂
3. v₁ + v₂/2
4. 1/v = 1/v₁ + 1/v₂

A body covers first 1/3 part of its journey with a velocity of 2 m/s, next 1/3 part with a velocity of 3 m/s and rest of the journey with a velocity 6m/s. The average velocity of the body will be

1. 3m/s
2. 11/3 m/s
3. 8/3 m/s
4. 4/3 m/s

A car runs at constant speed on a circular track of radius 100 m taking 62.8 s on each lap. What is the average speed and average velocity on each complete lap? (π = 3.14)

1. velocity 10m/s, speed 10 m/s
2. velocity zero, speed 10 m/s
3. velocity zero, speed zero
4. velocity 10 m/s, speed zero

The displacement of a body is given by 2s = gt2 where g is a constant. The velocity of the body at any time t is:

1. gt
2. gt/2
3. gt²/2
4. gt³/6

A stone is thrown vertically upward with an initial speed u from the top of a tower, reaches the ground with a speed 3u. The height of the tower is:

1. 3u²/g
2. 4u²/g
3. 6u²/g
4. 9u²/g

A particle starts from rest with uniform acceleration a. Its velocity after n seconds is v. The displacement of the particle in the last two seconds is :

1. 2v(n-1)/n
2. v(n-1)/n
3. v(n+1)/n
4. 2v(2n+1)/n

A body starts from rest and is uniformly acclerated for 30 s. The distance travelled in the first 10 s is x1, next 10 s is x2 and the last 10 s is x3. Then x1 : x2 : x3 is the same as

1. 1 : 2 : 4
2. 1 : 2 : 5
3. 1 : 3 : 5
4. 1 : 3 : 9

A ball is dropped from the top of a building. The ball takes 0.5 s to fall past the 3 m height of a window some distance from the top of the building. If the speed of the ball at the top and at the bottom of the window are vT and vB respectively, then (g = 9.8 m/sec²)

1. v_T + v_B = 12 ms^-1
2. v_T – v_B = 4.9 ms^-1
3. v_Bv_T = 1 ms^-1
4. v_B/v_T = 1 ms^-1

A stone is released from an elevator going up with an acceleration a and speed u. The acceleration and speed of the stone just after the release is

1. a upward, zero
2. (g-a) upward, u
3. (g-a) downward, zero
4. g downward, u

The initial velocity of a particle is given by u (at t = 0) and the acceleration by f, where f = at (here t is time and a is constant). Which of the following relation is valid?

1. v = u + at²
2. v = u + at²/2
3. v = u + at
4. v = u

A stone is dropped into a well in which the level of water is h below the top of the well. If v is velocity of sound, the time T after dropping the stone at which the splash is heard is given by

1. T = 2h/v
2. T = √2h/g + h/v
3. T = √2h/g + h/2v
4. T = √h/2g + 2h/v

A student determined to test the law of gravity for himself walks off a sky scraper 320 m high with a stopwatch in hand and starts his free fall (zero initial velocity). 5 second later, superman arrives at the scene and dives off the roof to save the student. What must be superman’s initial velocity in order that he catches the student just before reaching the ground ? [Assume that the superman’s acceleration is that of any freely falling body.] (g = 10 m/s²)

1. 98 m/s
2. 275/3 m/s
3. 187/2 m/s
4. It is not possible

In the above question, what must be the maximum height of the skyscraper so that even superman cannot save him.

1. 65 m
2. 85 m
3. 125 m
4. 145 m

Two particles held at different heights a and b above the ground are allowed to fall from rest. The ratio of their velocities on reaching the ground is :

1. a : b
2. √a : √b
3. a² : b²
4. a³ : b³

In the displacement–time graph of a moving particle is shown, the instantaneous velocity of the particle is negative at the point :

1. C
2. D
3. E
4. F

The variation of velocity of a particle moving along a straight line is shown in the figure. The distance travelled by the particle in 4 s is :

1. 25 m
2. 30 m
3. 55 m
4. 60 m

A particle starts from rest and moves along a straight line with constant acceleration. The variation of velocity v with displacement S is :

1. A
2. B
3. C
4. D

The displacement time graphs of two particles A and B are straight lines making angles of respectively 30° and 60° with the time axis. If the velocity of A is v_A and that of B is v_B, then the value of v_A/v_B is

1. 1/2
2. 1/√3
3. √3
4. 1/3

Starting from rest at t = 0, a car moves in a straight line with an acceleration given by the accompanying graph. The speed of the car at t = 3 s is :

1. 1 ms^–1
2. 2 ms^–1
3. 6.0 ms^–1
4. 10.5 ms^–1