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

HARD

Earn 100

STATEMENT-1: Gas ejected from the rocket will never exert thrust on the rocket if the ejected gas and the rocket move in the same direction.

STATEMENT-2: If the thrust force is to be exerted on the rocket in its direction of motion, the ejected gas (w.r.t. rocket) must move opposite to the velocity of rocket (w.r.t. ground).

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

Important Questions on Laws of Motion

Learn and Prepare for any exam you want !