Physics - Laws Motion - Quiz-3

A particle of mass 0.3 kg is subjected to a force F = –kx with k = 15 N/m. What will be its initial acceleration if it is released from a point 20 cm away from the origin

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5 m/s²
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10 m/s²
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3 m/s²
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15 m/s²

An elevator weighing 6000 kg is pulled upward by a cable with an acceleration of 5 ms^–2. Taking g to be 10 ms^–2, then the tension in the cable is

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6000 N
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9000 N
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60000 N
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90000 N

The ratio of the weight of a man in a stationary lift and when it is moving downward with uniform acceleration ‘a’ is 3 : 2. The value of ‘a’ is (g-Acceleration due to gravity of the earth)

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$\frac{3}{2} g$
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$\frac{g}{3}$
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$\frac{2}{3} g$
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g

If force on a rocket having exhaust velocity of 300 m/sec is 210 N, then rate of combustion of the fuel is

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0.7 kg/s
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1.4 kg/s
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0.07 kg/s
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10.7 kg/s

In an elevator moving vertically up with an acceleration g, the force exerted on the floor by a passenger of mass M is:

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Mg
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$\frac{1}{2} M g$
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Zero
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2 Mg

A 5000 kg rocket is set for vertical firing. The exhaust speed is 800 ms^–1. To give an initial upward acceleration of 20 ms^–2, the amount of gas ejected per second to supply the needed thrust will be (g = 10 ms^–2)

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127.5 kg s^–1
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187.5 kg s^–1
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185.5 kg s^–1
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137.5 kg s^–1

If a person with a spring balance and a body hanging from it goes up and up in an aeroplane, then the reading of the weight of the body as indicated by the spring balance will

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Go on increasing
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Go on decreasing
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First increase and then decrease
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Remain the same

Two balls of masses m₁ and m₂ are separated from each other by a powder charge placed between them. The whole system is at rest on the ground. Suddenly the powder charge explodes and masses are pushed apart. The mass m₁ travels a distance s₁ and stops. If the coefficients of friction between the balls and ground are same, the mass m₂ stops after travelling the distance

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$s_{2} = \frac{m_{1}}{m_{2}} s_{1}$
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$s_{2} = \frac{m_{2}}{m_{1}} s_{1}$
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$s_{2} = \frac{m_{1}^{2}}{m_{2}^{2}} s_{1}$
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$s_{2} = \frac{m_{2}^{2}}{m_{1}^{2}} s_{1}$

A force vector applied on a mass is represented as $\vec{F} = 6 \hat{i} - 8 \hat{j} + 10 \hat{k}$ and accelerates with 1 m/s². What will be the mass of the body?

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$10 \sqrt{2} k g$
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$2 \sqrt{10} k g$
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10 kg
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20 kg

A cricket ball of mass 250 g collides with a bat with velocity 10 m/s and returns with the same velocity within 0.01 second. The force acted on bat is

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25 N
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50 N
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250 N
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500 N

A pendulum bob of mass 50 gm is suspended from the ceiling of an elevator. The tension in the string if the elevator goes up with uniform velocity is approximately

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0.30 N
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0.40 N
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0.42 N
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0.50 N

The average force necessary to stop a bullet of mass 20 g moving with a speed of 250 m/s, as it penetrates into the wood for a distance of 12 cm is

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2.2 × 10³ N
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3.2 × 10³ N
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4.2 × 10³ N
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5.2 × 10³ N

A man measures time period of a pendulum (T) in stationary lift. If the lift moves upward with acceleration $\frac{g}{4},$ then new time period will be

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$\frac{2 T}{\sqrt{5}}$
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$\frac{\sqrt{5} T}{2}$
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$\frac{\sqrt{5}}{2 T}$
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$\frac{2}{\sqrt{5} T}$

If rope of lift breaks suddenly, the tension exerted by the surface of lift (a = acceleration of lift)

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mg
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m(g + a)
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m(g – a)
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0

A lift of mass 1000 kg is moving with an acceleration of 1 m/s² in the upward direction. Tension developed in the string, which is connected to the lift, is:

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9,800 N
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10,000 N
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10,800 N
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11,000 N

A lift accelerated downward with acceleration 'a'. A man in the lift throws a ball upward with acceleration a₀(a₀ < a). Then acceleration of ball observed by an observer, which is on earth, is

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(a + a₀) upward
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(a – a₀) upward
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(a + a₀) downward
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(a – a₀) downward

A lift is moving down with acceleration a. A man in the lift drops a ball inside the lift. The acceleration of the ball as observed by the man in the lift and a man standing stationary on the ground are respectively

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g, g
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g – a, g – a
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g – a , g
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a, g

A monkey of mass 20kg is holding a vertical rope. The rope will not break when a mass of 25 kg is suspended from it but will break if the mass exceeds 25 kg. What is the maximum acceleration with which the monkey can climb up along the rope (g = 10 m/s²)

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10 m/s²
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25 m/s²
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2.5 m/s²
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5 m/s²

A plumb line is suspended from a ceiling of a car moving with horizontal acceleration of a. What will be the angle of inclination with vertical

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tan^–1(a/g)
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tan^–1(g/a)
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cos^–1(a/g)
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cos^–1(g/a)

A body of mass 2 kg has an initial velocity of 3 meters per second along OE and it is subjected to a force of 4 N in a direction perpendicular to OE. The distance of the body from O after 4 seconds will be

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12 m
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20 m
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8 m
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48 m

A block of mass m is placed on a smooth wedge of inclination θ. The whole system is accelerated horizontally so that the block does not slip on the wedge. The force exerted by the wedge on the block (g is acceleration due to gravity) will be

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$m g \cos θ$
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$m g \sin θ$
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mg
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$m g / \cos θ$

The linear momentum p of a body moving in one dimension varies with time according to the equation p = a + bt² where a and b are positive constants. The net force acting on the body is

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A constant
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Proportional to t²
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Inversely proportional to t
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Proportional to t

A man of weight 80 kg is standing in an elevator which is moving with an acceleration of 6 m/s² in upward direction. The apparent weight of the man will be (g = 10 m/s²)

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1480 N
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1280 N
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1380 N
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None of these

N bullets each of mass m kg are fired with a velocity v ms^–1 at the rate of n bullets per second upon a wall. The reaction offered by the wall to the bullets is given by:

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nmv
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$\frac{N m v}{n}$
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$n \frac{N m}{v}$
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$n \frac{N v}{m}$

With what minimum acceleration can a fireman slides down a rope while breaking strength of the rope is $\frac{2}{3}$ of his weight

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$\frac{2}{3} g$
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g
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$\frac{1}{3} g$
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Zero

A ball of mass m moves with speed v and it strikes normally with a wall and reflected back normally, if its time of contact with wall is t then find force exerted by ball on wall

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$\frac{2 m v}{t}$
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$\frac{m v}{t}$
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mvt
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$\frac{m v}{2 t}$

A body of mass 5 kg starts from the origin with an initial velocity $\vec{u} = 30 \hat{i} + 40 \hat{j} m s^{- 1}$ . If a constant force $\vec{F} = - (\hat{i} + 5 \hat{j}) N$ acts on the body, the time in which the y–component of the velocity becomes zero is

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5 seconds
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20 seconds
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40 seconds
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80 seconds

A ball of mass 0.5 kg moving with a velocity of 2 m/sec strikes a wall normally and bounces back with the same speed. If the time of contact between the ball and the wall is one millisecond, the average force exerted by the wall on the ball is:

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2000 N
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1000 N
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5000 N
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125 N

A particle moves in the XY-plane under the action of a force F such that the components of its linear momentum p at any time t are $p_{x} = 2 \cos t$ , $p_{y} = 2 \sin t$ . The angle between F and p at time t will be:

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90°
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0°
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180°
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30°

A satellite in force-free space sweeps stationary interplanetary dust at a rate $d M / d t = α v$ where M is the mass, v is the velocity of the satellite and $α$ is a negative constant. What is the deacceleration of the satellite?

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$- 2 α v^{2} / M$
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$- α v^{2} / M$
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$+ α v^{2} / M$
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$- α v^{2}$

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Practice Physics Quiz Questions and Answers

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Practice Physics Quiz Questions and Answers

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