Motion Test

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Motion Test - 20

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Weekly Quiz Competition

Question 1
1 / -0

If the displacement of an object is proportional to square of time, then the object moves with

A
uniform velocity

B
uniform acceleration

C
increasing acceleration

D
decreasing acceleration

Solution

When the rate of change of velocity with time of a body is constant then the object is said to be uniformly accelerated.
Or in other words in uniform acceleration, the displacement of an object is proportional to square of time.
Question 2
1 / -0

Velocity of a body at rest is always

A
Unity

B
Negative

C
Zero

D
Infinite

Solution

When a body is at rest , the displacement is zero
$$v = \dfrac{s}{t} $$ (s is zero)
Therefore $$v = \dfrac{0}{t} $$
$$v = 0 $$
Question 3
1 / -0

A body initially moving with a velocity of $$5\ ms^{-1}$$ attains a velocity of $$25\ ms^{-1}$$ in $$5\ s$$, find the acceleration of body in $$ms^{-2}.$$

A
$$8ms^{-2}$$

B
$$7ms^{-2}$$

C
$$4ms^{-2}$$

D
$$3ms^{-2}$$

Solution

Acceleration $$ = \dfrac{\text{Final velocity - initial velocity}}{\text{time taken}}$$

Final velocity $$v = 25 m/s $$
Initial velocity $$u = 5 m/s $$
a $$= \dfrac{25 - 5}{5} m/s^2$$
a $$= 4 m/s^2 $$
Question 4
1 / -0

A ball is thrown vertically upwards with a speed of $$30\ ms^{-1}$$. The equation for velocity is (Take g= $$10\ ms^{-2}$$)

A
$$v=30 + 10t$$

B
$$v=30 - 10t$$

C
$$v= -10t$$

D
$$v= 10t$$

Solution

$$u=30ms^{-1} ; g=-10ms^{-2}$$
$$v=u+gt$$
$$v=30-10t $$ (As g acting downward so g$$=-10ms^{-2})$$
hence,option B is correct.
Question 5
1 / -0

The velocity of a body can change

A
if its acceleration is zero.

B
if its acceleration is non-zero.

C
Both A & B

D
None of the above.

Solution

Acceleration is defined as change of velocity in unit time. So if acceleration is zero, there is no change of velocity, the body is moving with a constant velocity.
Question 6
1 / -0

Physical quantity corresponding to the rate of change of displacement is

A
Speed

B
Velocity

C
Acceleration

D
Retardation

Solution

Velocity is the rate of change of displacement
Question 7
1 / -0

If two masses $$ m_1,\ m_2$$ are thrown vertically upwords with the same velocity, what is the difference in the maximum height gained by them? ($$ m_1 > m_2$$)

A
$$m_1$$

B
$$m_2$$

C
Both reach same height

D
None of the above

Solution

Height is given by,
$$h = ut - (1/2) gt^2$$
Since they are thrown with the same velocity, they will reach the same height.
Question 8
1 / -0

The expression for the velocity when a body dropped from a height reaches the ground is

A
$$V^2 =2s$$

B
$$V^2=2gs$$

C
$$V=2gs$$

D
$$V^2=\frac{gs}{2}$$

Solution

When a body is dropped from a height h its initial velocity u is zero. Let the final velocity on reaching the ground be V.
From the formula,
$$V^2=U^2+2gs$$, here u=0
$$V^2=2gs$$
Answer (B) $$V^2=2gs$$
Question 9
1 / -0

Unit for the rate of change of velocity is

A
m / s

B
$$m / s^2$$

C
N s

D
N / s

Solution

Velocity units $$ = m/s$$
Acceleration is the rate of change of velocity
a $$= \dfrac{change \ in \ velocity }{time } $$
Therefore SI units of acceleration is $$ms^{-1}/s = \dfrac{m}{s^2} $$
Question 10
1 / -0

The displacement of a body which starts from rest, and moving with an acceleration of $$1\ ms^{-2}$$ at the end of $$5\ s$$ in m is:

A
12.5

B
25

C
7.5

D
15

Solution

Using the equations of motion
$$ s = ut + \frac{1}{2} at^2$$
$$u = 0$$ since the body starts from rest
$$ a = 1 m/s^2 $$ and time $$ t = 5s$$

$$s = \frac{1}{2} \times 5^2 $$
$$s = 12.5 m $$

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Re-Attempt Weekly Quiz Competition

Motion Test - 20

Result

Motion Test - 20

Score

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Rank

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SHARING IS CARING

Question 1

uniform velocity

uniform acceleration

increasing acceleration

decreasing acceleration

Solution

Question 2

Unity

Negative

Zero

Infinite

Solution

Question 3

$$8ms^{-2}$$

$$7ms^{-2}$$

$$4ms^{-2}$$

$$3ms^{-2}$$

Solution

Question 4

$$v=30 + 10t$$

$$v=30 - 10t$$

$$v= -10t$$

$$v= 10t$$

Solution

Question 5

if its acceleration is zero.

if its acceleration is non-zero.

Both A & B

None of the above.

Solution

Question 6

Speed

Velocity

Acceleration

Retardation

Solution

Question 7

$$m_1$$

$$m_2$$

Both reach same height

None of the above

Solution

Question 8

$$V^2 =2s$$

$$V^2=2gs$$

$$V=2gs$$

$$V^2=\frac{gs}{2}$$

Solution

Question 9

m / s

$$m / s^2$$

N s

N / s

Solution

Question 10

12.5

25

7.5

15

Solution

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