EASY

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Assertion: A body, whatever its motion is always at rest in a reference frame that is fixed to the body itself.

Reason: The relative velocity of a body with respect to itself is always zero.

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Important Questions on Laws of Motion

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

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})

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 ?

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:

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

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

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}

]

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?

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

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 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:

EASY

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

A man weighing

80 kg

, stands on a weighing scale in a lift that is moving upwards with a uniform acceleration of

5 m s^{- 2}

. What would be the reading on the scale?

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

EASY

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

A rocket with a lift-off mass

3 .5 \times 1 0^{4} kg

is blasted upwards with an initial acceleration of

10 m s^{- 2}

. Then the initial thrust of the blast is

EASY

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

A physics professor in his car drops a coffee mug while moving at a constant velocity of

9.8 m s^{- 1}

along the highway. The professor notices that it only takes a half a second for the mug to drop straight down to the floor of his car. A student standing alongside the road sees the mug moving in a parabola with respect to her. What time does she measure for the mug to hit the floor of the car?

HARD

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

A circular disc with a groove along its diameter is placed horizontally on a rough surface. A block of mass

1 kg

is placed as shown. The co-efficient of friction between the block and all surfaces of groove and horizontal surface in contact is

μ = \frac{2}{5} .

The disc has an acceleration of

25 {ms}^{- 2}

towards left. Find the acceleration of the block with respect to disc. Given,

\cos θ = \frac{4}{5}, \sin θ = \frac{3}{5}

Question Image

MEDIUM

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

A block is kept on a smooth inclined plane of the angle of inclination

30 °

that moves with a constant acceleration so that the block does not slide relative to the inclined plane. Let

F_{1}

be the contact force between the block and the plane. Now the inclined plane stops and let

F_{2}

be the contact force between the two in this case. Then

\frac{F_{1}}{F_{2}}

MEDIUM

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

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

HARD

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

Two blocks of mass

m_{1} = 10 kg

and

m_{2} = 5 kg

, connected to each other by a massless inextensible string of length

0.3 m

are placed along a diameter of a turn table. The coefficient of friction between the table and

m_{1}

0.5

while there is no friction between

m_{2}

and the table. The table is rotating with an angular velocity of

10 {rads}^{- 1}

about a vertical axis passing through its centre

O

. The masses are placed along the diameter of the table on either side of the centre

O

such that the mass

m_{1}

is at a distance of

0.124 m

from

O

. The masses are observed to be at rest with respect to an observer on the turn table. Calculate the frictional force on

m_{1}

EASY

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

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 –

Assertion: A body, whatever its motion is always at rest in a reference frame that is fixed to the body itself. Reason: The relative velocity of a body with respect to itself is always zero.

Important Questions on Laws of Motion

Learn and Prepare for any exam you want !

Assertion: A body, whatever its motion is always at rest in a reference frame that is fixed to the body itself.

Reason: The relative velocity of a body with respect to itself is always zero.