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

Earn 100

A space-ship travelling in the interstellar medium is picking up dust at a rate $\frac{d M}{d t} = α v$ , where $α$ is a positive constant, $v$ is the instantaneous velocity and $M$ is the total mass of the space-ship at any instant. The instantaneous acceleration of the space-ship is

50% studentsanswered this correctly

Important Questions on Laws of Motion

MEDIUM

Physics>Mechanics>Laws of Motion>Newton’s Laws of Motion

Calculate the acceleration of the block and trolly system shown in the figure. The coefficient of kinetic friction between the trolly and the surface is $0.05 .$ ( $g = 10 m s^{- 2},$ mass of the string is negligible and no other friction exists).

Question Image

EASY

Physics>Mechanics>Laws of Motion>Newton’s Laws of Motion

A machine gun has a mass

5 kg

. It fires

50

gram bullets at the rate of

30

bullets per minute at a speed of

400 m s^{- 1} .

What force is required to keep the gun in position?

EASY

Physics>Mechanics>Laws of Motion>Newton’s Laws of Motion

Two bodies of mass

4 kg

and

6 kg

are tied to the ends of a massless string. The string passes over a pulley which is frictionless (see figure). The acceleration of the system in terms of acceleration due to gravity

(g)

is:

MEDIUM

Physics>Mechanics>Laws of Motion>Newton’s Laws of Motion

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>Laws of Motion>Newton’s Laws of Motion

A balloon has a mass of

10

gram in air. The air escapes from the balloon at a uniform rate with a velocity of

5 cm s^{- 1}

and the balloon shrinks completely in

2.5 s

. The average force acting on the balloon will be

HARD

Physics>Mechanics>Laws of Motion>Newton’s Laws of Motion

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

MEDIUM

Physics>Mechanics>Laws of Motion>Newton’s Laws of Motion

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 ?

EASY

Physics>Mechanics>Laws of Motion>Newton’s Laws of Motion

A force of

0.03 N

acts on a body of mass

0.5 kg

, which is initially at rest, for a duration of

10

seconds. Then find the momentum acquired by the body.

EASY

Physics>Mechanics>Laws of Motion>Newton’s Laws of Motion

A balloon has mass of

10 g

in air. The air escapes from the balloon at a uniform rate with velocity

4.5 cm s^{- 1}

. If the balloon shrinks in

5 s

completely. Then, the average force acting on that balloon will be (in dyne).

MEDIUM

Physics>Mechanics>Laws of Motion>Newton’s Laws of Motion

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

MEDIUM

Physics>Mechanics>Laws of Motion>Newton’s Laws of Motion

A steam of water flowing horizontally with a speed of

25 {ms}^{- 1}

gushes out of a tube of cross-section area

10^{- 3} m^{2}

, and hits at a vertical wall nearby. What is the force exerted on the wall by the impact of water ?

EASY

Physics>Mechanics>Laws of Motion>Newton’s Laws of Motion

5000 kg

rocket is set for vertical firing. The exhaust speed is

800 m s^{- 1}

. To give an initial upward acceleration of

20 m s^{- 2}

, the amount of gas ejected per second to supply the needed thrust will be:

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

EASY

Physics>Mechanics>Laws of Motion>Newton’s Laws of Motion

The time taken by a force of

2 N

to produce a change of momentum of

0.4 kg m s^{- 1}

in a

MEDIUM

Physics>Mechanics>Laws of Motion>Newton’s Laws of Motion

An object takes

n

times as much time to slide down a

45 °

rough inclined plane as it takes to slide down a perfectly smooth

45 °

inclined plane. The coefficient of kinetic friction between the rough plane and the object is

MEDIUM

Physics>Mechanics>Laws of Motion>Newton’s Laws of Motion

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?

EASY

Physics>Mechanics>Laws of Motion>Newton’s Laws of Motion

A machine gun can fire

200 bullets \min^{- 1}

. If

35 g

bullets are fired at a speed of

750 m s^{- 1}

, the average force exerted by the gun on the bullets is,

MEDIUM

Physics>Mechanics>Laws of Motion>Newton’s Laws of Motion

Two blocks of masses

m_{1}

and

m_{2}

are suspended by a massless string passing over a smooth pulley. If the acceleration of the system is

\frac{g}{8},

then the ratio of the masses

\frac{m_{2}}{m_{1}} =

HARD

Physics>Mechanics>Laws of Motion>Newton’s Laws of Motion

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>Laws of Motion>Newton’s Laws of Motion

A spaceship in space sweeps stationary interplanetary dust. As a result, its mass increases at a rate

\frac{d M (t)}{d t} = b v^{2} (t),

where

v (t)

is its instantaneous velocity. The instantaneous acceleration of the satellite is:

EASY

Physics>Mechanics>Laws of Motion>Newton’s Laws of Motion

In a tug war contest, two man pull on a horizontal rope from opposite sides. The winner will be the man who

A space-ship travelling in the interstellar medium is picking up dust at a rate dMdt=αv, where α is a positive constant, v is the instantaneous velocity and M is the total mass of the space-ship at any instant. The instantaneous acceleration of the space-ship is

Important Questions on Laws of Motion

Learn and Prepare for any exam you want !

A space-ship travelling in the interstellar medium is picking up dust at a rate $\frac{d M}{d t} = α v$ , where $α$ is a positive constant, $v$ is the instantaneous velocity and $M$ is the total mass of the space-ship at any instant. The instantaneous acceleration of the space-ship is