A particle moving in the xy -plane experiences a velocity dependent force F → = k υ y i ^ + υ x j ^ , where υ x and υ y are the x and y components of its velocity υ → . If a → is the acceleration of the particle, then which of the following statements is true for the particle ?

quantity υ → × a → is constant in time

F → arises due to a magnetic field

kinetic energy of particle is constant in time

quantity υ → . a → is constant in time

EASY

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Assertion: The apparent weight of a body in an elevator moving with some downward acceleration is less than the actual weight of body.

Reason: The part of the weight is spent in producing downward acceleration, when body is in elevator.

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Important Questions on Newton's Laws of Motion

EASY

Physics>Mechanics>Newton's Laws of Motion>Non-inertial Frame and Pseudo Force

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

HARD

Physics>Mechanics>Newton's Laws of Motion>Non-inertial Frame and Pseudo Force

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>Newton's Laws of Motion>Non-inertial Frame and Pseudo Force

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>Newton's Laws of Motion>Non-inertial Frame and Pseudo Force

A particle moving in the

xy

-plane experiences a velocity dependent force

\vec{F} = k (υ_{y} \hat{i} + υ_{x} \hat{j})

, where

υ_{x}

and

υ_{y}

are the

x

and

y

components of its velocity

\vec{υ}

. If

\vec{a}

is the acceleration of the particle, then which of the following statements is true for the particle ?

MEDIUM

Physics>Mechanics>Newton's Laws of Motion>Non-inertial Frame and Pseudo Force

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

HARD

Physics>Mechanics>Newton's Laws of Motion>Non-inertial Frame and Pseudo Force

A ball is thrown upward with an initial velocity

V_{0}

from the surface of the earth. The motion of the ball is affected by a drag force equal to

m γ v^{2}

(where

m

is mass of the ball,

v

is its instantaneous velocity and

γ

is a constant). Time taken by the ball to rise to its zenith is:

MEDIUM

Physics>Mechanics>Newton's Laws of Motion>Non-inertial Frame and Pseudo Force

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})

HARD

Physics>Mechanics>Newton's Laws of Motion>Non-inertial Frame and Pseudo Force

A ball of mass

0.45 kg

which is initially at rest is hit by a bat. The bat remains in contact with the ball for

3 \times 10^{- 3} s

. During this time period the force on the ball by the bat is given as

F (t) = [(α \times 10^{6}) t - (β \times 10^{9}) t^{2}] N

where

α

and

β

are constants. The ball's speed immediately as it loses contact with the bat is

20 m s^{- 1}

. The correct relation between

α

and

β

HARD

Physics>Mechanics>Newton's Laws of Motion>Non-inertial Frame and Pseudo Force

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>Newton's Laws of Motion>Non-inertial Frame and Pseudo Force

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?

HARD

Physics>Mechanics>Newton's Laws of Motion>Non-inertial Frame and Pseudo Force

A body of mass

m

is moving in a straight line with momentum

p

. Starting at time

t = 0

, a force

F = a t

acts in the same direction on the moving particle during time interval of

T

. So that its momentum changes from

p

2 p

. The value of

T

HARD

Physics>Mechanics>Newton's Laws of Motion>Non-inertial Frame and Pseudo Force

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>Newton's Laws of Motion>Non-inertial Frame and Pseudo Force

The force on a body of mass

1 kg

(20 \hat{i} + 10 \hat{j}) N

. If it starts from rest, then the position of the body at time

t = 2 s,

EASY

Physics>Mechanics>Newton's Laws of Motion>Non-inertial Frame and Pseudo Force

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:

MEDIUM

Physics>Mechanics>Newton's Laws of Motion>Non-inertial Frame and Pseudo Force

When will a body of mass

20 kg

moving at

15 m s^{- 1},

subjected to a retarding force of

100 N

, come to rest?

HARD

Physics>Mechanics>Newton's Laws of Motion>Non-inertial Frame and Pseudo Force

The graph below shows the variation of a force $F$ with time $t$ on a body which is moving in a straight line. Dependence of force on time is $F \propto t^{n}$ . Initially body is at rest.

Question Image
If the speed of the object is $2 m / s$ at $3 s$ , then the speed at $4 s$ will be approximately (in $m / s$ )

MEDIUM

Physics>Mechanics>Newton's Laws of Motion>Non-inertial Frame and Pseudo Force

Two horizontal forces

{\vec{F}}_{1}

and

{\vec{F}}_{2}

act on a ball of mass

8 kg

. The forces are such that

{\vec{F}}_{1} = (14 N) \hat{i}

and

|{\vec{F}}_{2}| = 20 N

. If the

x

component of velocity

(v_{x})

changes linearly by

3 m s^{- 1}

1 \sec

, the angle between two forces is

EASY

Physics>Mechanics>Newton's Laws of Motion>Non-inertial Frame and Pseudo Force

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>Newton's Laws of Motion>Non-inertial Frame and Pseudo Force

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>Newton's Laws of Motion>Non-inertial Frame and Pseudo Force

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:

Assertion: The apparent weight of a body in an elevator moving with some downward acceleration is less than the actual weight of body. Reason: The part of the weight is spent in producing downward acceleration, when body is in elevator.

Important Questions on Newton's Laws of Motion

Learn and Prepare for any exam you want !

Assertion: The apparent weight of a body in an elevator moving with some downward acceleration is less than the actual weight of body.

Reason: The part of the weight is spent in producing downward acceleration, when body is in elevator.