A particle moves so that its position vector is given by r → = c o s ω t x ^ + s i n ω t y ^ , where ω is a constant. Which of the following is true?

Velocity is perpendicular to r → and acceleration is directed towards the origin.

Velocity and acceleration both are perpendicular to r → .

Velocity and acceleration both are parallel to r → .

Velocity is perpendicular to r → and acceleration is directed away from the origin.

MEDIUM

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Describe the process of calculating the average velocity from the position-time graph for a given time interval.

Important Questions on Motion in a Straight Line

MEDIUM

Physics>Mechanics>Motion in a Straight Line>Instantaneous Velocity and Speed

A particle is moving such that its position coordinates

(x, y)

are

(2 m, 3 m)

at time

t = 0,

(6 m, 7 m)

at time

t = 2 s

and

(13 m, 14 m)

at time

t = 5 s

. The average velocity vector

({\vec{V}}_{a v})

from

t = 0

t = 5 s

is:

MEDIUM

Physics>Mechanics>Motion in a Straight Line>Instantaneous Velocity and Speed

The

x

and

y

coordinates of the particle at any time are

x = 5 t - 2 t^{2}

and

y = 10 t

respectively, where

x

and

y

are in meters and

t

is in seconds. The acceleration of the particle at

t = 2 s

EASY

Physics>Mechanics>Motion in a Straight Line>Instantaneous Velocity and Speed

Average velocity of a particle executing SHM in one complete vibration is

MEDIUM

Physics>Mechanics>Motion in a Straight Line>Instantaneous Velocity and Speed

The displacement of a particle moving with uniform acceleration in time

t

is given by

S = 30 t + 5 t^{2}

, its initial velocity is _____

EASY

Physics>Mechanics>Motion in a Straight Line>Instantaneous Velocity and Speed

In $1.0 s,$ a particle goes from $A to B$ moving in a semicircle of $1.0 m$ radius (as shown in the figure)

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The magnitude of the average velocity is

MEDIUM

Physics>Mechanics>Motion in a Straight Line>Instantaneous Velocity and Speed

The displacement

x

(in meter) of a particle of mass

m

(in kg) moving in one dimension under the action of a force, is related to time

t

(in sec) by

t = \sqrt{x} + 3

. The displacement of the particle when its velocity is zero, will be

MEDIUM

Physics>Mechanics>Motion in a Straight Line>Instantaneous Velocity and Speed

Consider an expanding sphere of instantaneous radius

R

whose total mass remains constant. The expansion is such that the instantaneous density

ρ

remains uniform throughout the volume. The rate of fractional change in density

(\frac{1}{ρ} \frac{d ρ}{d t})

is constant. The velocity

v

of any point on the surface of the expanding sphere is proportional to

MEDIUM

Physics>Mechanics>Motion in a Straight Line>Instantaneous Velocity and Speed

Consider a particle moving along the positive direction of

X

-axis. The velocity of the particle is given by

v = α \sqrt{x}

(

α

is a positive constant). At time

t = 0

, if the particle is located at

x = 0

, the time dependence of the velocity and the acceleration of the particle are respectively.

MEDIUM

Physics>Mechanics>Motion in a Straight Line>Instantaneous Velocity and Speed

The displacement-time graphs of two moving particles make angles of $30 °$ and $45 °$ with the $x$ -axis as shown in the figure. The ratio of their respective velocity is:

Question Image

MEDIUM

Physics>Mechanics>Motion in a Straight Line>Instantaneous Velocity and Speed

A particle moves so that its position vector is given by

\vec{r} = c o s ω t \hat{x} + s i n ω t \hat{y}

, where

ω

is a constant. Which of the following is true?

MEDIUM

Physics>Mechanics>Motion in a Straight Line>Instantaneous Velocity and Speed

The acceleration at the end of

2 s

, of a particle whose motion is represented by the equation

S = 4 t^{3} - 8 t^{2} + 5 t + 4

is ______

EASY

Physics>Mechanics>Motion in a Straight Line>Instantaneous Velocity and Speed

A particle shows the distance-time curve as shown in the figure. The maximum instantaneous velocity of the particle is around the point.

Question Image

EASY

Physics>Mechanics>Motion in a Straight Line>Instantaneous Velocity and Speed

A fly is in rectilinear motion as described by the graph. The average speed of the fly is

Question Image

HARD

Physics>Mechanics>Motion in a Straight Line>Instantaneous Velocity and Speed

The position of a particle as a function of time

t,

is given by

x (t) = a t + b t^{2} - c t^{3}

where

a, b

and

c

are constants. When the particle has zero acceleration, then its velocity will be:

MEDIUM

Physics>Mechanics>Motion in a Straight Line>Instantaneous Velocity and Speed

Consider a car initially at rest, starts to move along a straight road first with acceleration

5 m s^{- 2},

then with uniform velocity and finally, decelerating at

5 m s^{- 2},

, before coming to a stop. Total time taken from start to end is

t = 25 s

. If the average velocity during that time is

72 km {hr}^{- 1},

the car moved with uniform velocity for a time of

EASY

Physics>Mechanics>Motion in a Straight Line>Instantaneous Velocity and Speed

If a particle's position is given by

x = 4 - 12 t + 3 t^{2}

where

t

is in the seconds and

x

in meters. What is its velocity at

t = 1 s

? Whether the particle is moving in positive

x

direction or negative

x

direction?

EASY

Physics>Mechanics>Motion in a Straight Line>Instantaneous Velocity and Speed

A car moves in positive

Y

-direction with velocity

v

proportional to distance travelled

y

v (y) \propto y^{β}

, where

β

is a positive constant. The car covers a distance

L

with average velocity

<v>

proportional to

L

<v> \propto L^{1 / 3}

. The constant

β

is given as

EASY

Physics>Mechanics>Motion in a Straight Line>Instantaneous Velocity and Speed

Two cars

P

and

Q

start from a point at the same time in a straight line and their positions are represented by

X_{P} (t) = a t + b t^{2}

and

X_{Q} (t) = f t - t^{2}

. At what time do the cars have the same velocity?

MEDIUM

Physics>Mechanics>Motion in a Straight Line>Instantaneous Velocity and Speed

A car covers the first half distance between two places at

40 kmph

and the other half at

60 kmph .

The average speed of the car is

EASY

Physics>Mechanics>Motion in a Straight Line>Instantaneous Velocity and Speed

The displacement of a body is given by

x = 4 t + 5 t^{3},

where

x

is in metre and

t

is in second. The difference between the average velocity of the body in the time-interval

t = 1 s

t = 2 s

and its instantaneous-velocity at

t = 1 s

Describe the process of calculating the average velocity from the position-time graph for a given time interval.

Important Questions on Motion in a Straight Line

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