A particle of mass m is initially at rest at the origin. It is subjected to a force and starts moving along the x - axis. Its kinetic energy changes with time as d K d t = γ t , where γ is a positive constant of appropriate dimensions. Which of the following statements is (are) true?

The distance of the particle from the origin increases linearly with time

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A spring balance is attached to the ceiling of a lift. A man hangs his bag on the spring and the spring reads $49 N$ , when the lift is stationary. If the lift moves downward with an acceleration of $5 m s^{- 2}$ , the reading of the spring balance will be

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Important Questions on Laws of Motion

EASY

Physics>Mechanics>Laws of Motion>Inertial and Non-inertial Frames of Reference

A person is standing in an elevator. In which situation, he experiences weight loss ?

HARD

Physics>Mechanics>Laws of Motion>Inertial and Non-inertial Frames of Reference

Two wooden blocks are moving on a smooth horizontal surface such that the block having mass $m$ remains stationary with respect to block of mass $M$ as shown in the figure below. The magnitude of the applied force $P$ is,

Question Image

EASY

Physics>Mechanics>Laws of Motion>Inertial and Non-inertial Frames of Reference

A block of mass

M

placed inside a box descends vertically with acceleration

a

. The block exerts a force equal to one-fourth of its weight on the floor of the box. The value of

a

will be

HARD

Physics>Mechanics>Laws of Motion>Inertial and Non-inertial Frames of Reference

A particle of mass

m

is initially at rest at the origin. It is subjected to a force and starts moving along the x - axis. Its kinetic energy changes with time as

\frac{d K}{d t} = γ t,

where

γ

is a positive constant of appropriate dimensions. Which of the following statements is (are) true?

MEDIUM

Physics>Mechanics>Laws of Motion>Inertial and Non-inertial Frames of Reference

A boy is standing on a weighing machine inside a lift. When the lift goes upwards with acceleration

\frac{g}{4},

the machine shows the reading

50 kg .

wt. When the lift goes downward with acceleration

\frac{g}{4},

the reading of the machine in

kg

wt

. would be

MEDIUM

Physics>Mechanics>Laws of Motion>Inertial and Non-inertial Frames of Reference

A mass of

10 kg

is suspended vertically by a rope from the roof. When a horizontal force is applied on the rope at some point, the rope deviated at an angle of

45 °

at the roof point. If the suspended mass is at equilibrium, the magnitude of the force applied is

(g = 10 m s^{- 2})

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Physics>Mechanics>Laws of Motion>Inertial and Non-inertial Frames of Reference

When a lift of mass

800 kg

is ascending with an acceleration of

5 m s^{- 2}

, the tension in its cable will be

______

take

(g = 10 m s^{- 2})

MEDIUM

Physics>Mechanics>Laws of Motion>Inertial and Non-inertial Frames of Reference

An elevator of mass

m

is connected to a rope which pulls the elevator up with a maximum acceleration equal to

a

. If the maximum bearable tension in the rope is

T

, then for a safe journey the minimum diameter of the rope is [

g

= acceleration due to gravity]

HARD

Physics>Mechanics>Laws of Motion>Inertial and Non-inertial Frames of Reference

A girl drops an apple from the window of a train which is moving on a straight track with speed increasing with a constant rate. The trajectory of the falling apple as seen by the girl is

EASY

Physics>Mechanics>Laws of Motion>Inertial and Non-inertial Frames of Reference

A plumb line is suspended from a ceiling of a car moving with horizontal acceleration

a

. What will be the angle of inclination with vertical?

MEDIUM

Physics>Mechanics>Laws of Motion>Inertial and Non-inertial Frames of Reference

A stream of water flowing horizontally with a speed of

15 m s^{- 1}

gushes out of a tube of cross-sectional area

10^{- 2} m^{2}

and hits a vertical wall nearby. The force exerted on the wall by the impact of water (assuming it does not rebound) is

HARD

Physics>Mechanics>Laws of Motion>Inertial and Non-inertial Frames of Reference

A particle is moving along the

x

-axis with its coordinate with time

t

given by

x (t) = 10 + 8 t - 3 t^{2} .

Another particle is moving along the

y

-axis with its coordinate as a function of time given by

y (t) = 5 - 8 t^{3} .

t = 1 s,

the speed of the second particle as measured in the frame of the first particle is given as

\sqrt{v} .

Then

v (i n m s^{- 1})

is ___________.

MEDIUM

Physics>Mechanics>Laws of Motion>Inertial and Non-inertial Frames of Reference

A rod of weight

W

is supported by two parallel knife edges

A

and

B

and is in equilibrium in a horizontal position. The knives are at a distance

d

from each other. The centre of mass of the rod is at distance

x

from

A

. the normal reaction on

A

is:

EASY

Physics>Mechanics>Laws of Motion>Inertial and Non-inertial Frames of Reference

A block

A

takes

2 s

to slide down a frictionless incline of

30 °

and length

l

, kept inside a lift going up with uniform velocity

v

. If the incline is changed to

45 °

, the time taken by the block, to slide down the incline, will be approximately:

EASY

Physics>Mechanics>Laws of Motion>Inertial and Non-inertial Frames of Reference

Three blocks A, B and C, of masses

4 kg, 2 kg

1 kg

and respectively, are in contact on a frictionless surface, as shown. If a force of

14 N

is applied on the

4 kg

block, then the contact force between A and B is:

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MEDIUM

Physics>Mechanics>Laws of Motion>Inertial and Non-inertial Frames of Reference

Two blocks

A

and

B

of masses

3 m

and

m

respectively are connected by a massless and inextensible string. The whole system is suspended by a massless spring as shown in figure. The magnitudes of acceleration of

A

and

B

immediately after the string is cut, are respectively
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HARD

Physics>Mechanics>Laws of Motion>Inertial and Non-inertial Frames of Reference

The machine as shown has $2$ rods of length $1 m$ connected by a pivot at the top. The end of one rod is connected to the floor by a stationary pivot and the end of the other rod has roller that rolls along the floor in a slot. As the roller goes back and forth, a $2 kg$ weight moves up and down. If the roller is moving towards right at a constant speed, the weight moves up with a :

Question Image

EASY

Physics>Mechanics>Laws of Motion>Inertial and Non-inertial Frames of Reference

A man weighing

60 kg

is in a lift moving down with an acceleration of

1.8 {ms}^{- 2}

. The force exerted by the floor on him is?

MEDIUM

Physics>Mechanics>Laws of Motion>Inertial and Non-inertial Frames of Reference

Two blocks

A

and

B

of masses

m_{A} = 1 k g

and

m_{B} = 3 k g

are kept on the table as shown in figure. The coefficients of friction between

A

and

B

0.2

and between

B

and the surface of the table is also

0.2 .

The maximum force

F

that can be applied on

B

horizontally, so that the block

A

does not slide over the block

B

is : [Take

g = 10 m / s^{2}

]

MEDIUM

Physics>Mechanics>Laws of Motion>Inertial and Non-inertial Frames of Reference

A rocket is fired vertically from the earth with an acceleration of 2g, where g is the gravitational acceleration. On an inclined plane inside the rocket, making an angle

θ

with the horizontal, a point object of mass m is kept. The minimum coefficient of friction

μ_{m i n}

between the mass and the inclined surface such that the mass does not move is:

A spring balance is attached to the ceiling of a lift. A man hangs his bag on the spring and the spring reads 49 N, when the lift is stationary. If the lift moves downward with an acceleration of 5 m s-2, the reading of the spring balance will be

Important Questions on Laws of Motion

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A spring balance is attached to the ceiling of a lift. A man hangs his bag on the spring and the spring reads $49 N$ , when the lift is stationary. If the lift moves downward with an acceleration of $5 m s^{- 2}$ , the reading of the spring balance will be