Motion in A Straight Line Test

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Motion in A Straight Line Test - 14

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Weekly Quiz Competition

Question 1
1 / -0

Unit of acceleration is

A
$$m/s$$

B
$$ms$$

C
$$m/s^2$$

D
none of these

Solution

acceleration $$ = \dfrac{dv}{dt}$$
Units of 'v' is m/s and 't' is seconds
Therefore units of acceleration is $$\dfrac{m}{s^2} $$
Question 2
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 3
1 / -0

If the velocity of a body does not change, its acceleration is

A
Zero

B
Infinite

C
Unity

D
None of these

Solution

Acceleration of a body is defined as the rate of change of the velocity of the body. Now since the velocity doesn't change at all, the rate of change will be zero.
So, acceleration = 0
Question 4
1 / -0

The velocity of an object increases at a constant rate from $$20 m s^{-1}$$ to $$50 m s^{-1}$$in 10 s. Find the acceleration.

A
$$-3 \,m \,s^{-2}$$

B
$$-30 \,m \,s^{-2}$$

C
$$30 \,m \,s^{-2}$$

D
$$3 \,m \,s^{-2}$$

Solution

Acceleration $$a=\dfrac {v-u}{t}=\dfrac{50 \ m s^{-1}-20 \ m s^{-1}}{10 s}$$
or $$ a=\dfrac{30 \ m s^{-1}}{10 s}$$
$$= 3 \ m s^{-2}$$
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

A bomb is released from a horizontal flying aeroplane .The trajectory of bomb as observed from ground is

A
a parabola

B
a straight line

C
a circle

D
a hyperbola

Solution

When thrown from aeroplane , it will have velocity in horizontal direction. Thus angle between velocity and acceleration (i.e. gravity) is neither 0 nor 180 so, it wil be pprojectile motion (i.e. parabola in shape).
Question 7
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 8
1 / -0

A block is released from rest at the top of a friction-less inclined plane 16 m long. It reaches the bottom 4 sec later. A second block is projected up the plane from the bottom. At the instant at which the block is released in such a way that it returns to the bottom simultaneously with the first block. The acceleration of each block on the incline is :

A
$$ 1 m/s^{2}$$

B
$$ 2 m/s^{2}$$

C
$$ 4 m/s^{2}$$

D
$$ 9.8 m/s^{2}$$

Solution

Acceleration of both the blocks will be the same on the inclined plane
Let it be '$$a$$'
So, according the the equation of motion
$$\frac { 1 }{ 2 } \times a\times { 4 }^{ 2 }=16\Rightarrow a=2m/{ s }^{ 2 }$$
Question 9
1 / -0

Which of the following is/are true about acceleration

A
Acceleration is defined as the rate of change of velocity.

B
Its SI unit is $$m/s^2$$.

C
Negative acceleration is called retardation

D
All the above.

Solution

Acceleration =$$\dfrac{Final\ velocity\ - Initial\ velocity }{time}$$

Its SI unit is =$$ms^{-1}/s=m/s^2$$

A negative acceleration acts opposite to the direction of motion of object and it reduces the velocity , it called retardation.
Question 10
1 / -0

An object is thrown vertically upwards and rises to a height of 10 m. Calculate the velocity with which the object was thrown upwards :

A
7 m/s

B
14 m/s

C
28 m/s

D
56 m/s

Solution

$$v^2=u^2+2as$$
$$0=u^2+2(-9.8)(10)$$
$$u= \sqrt{2\times9.8\times10}= 14 m/s$$

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Re-Attempt Weekly Quiz Competition

Motion in A Straight Line Test - 14

Result

Motion in A Straight Line Test - 14

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SHARING IS CARING

Question 1

$$m/s$$

$$ms$$

$$m/s^2$$

none of these

Solution

Question 2

$$8ms^{-2}$$

$$7ms^{-2}$$

$$4ms^{-2}$$

$$3ms^{-2}$$

Solution

Question 3

Zero

Infinite

Unity

None of these

Solution

Question 4

$$-3 \,m \,s^{-2}$$

$$-30 \,m \,s^{-2}$$

$$30 \,m \,s^{-2}$$

$$3 \,m \,s^{-2}$$

Solution

Question 5

if its acceleration is zero.

if its acceleration is non-zero.

Both A & B

None of the above.

Solution

Question 6

a parabola

a straight line

a circle

a hyperbola

Solution

Question 7

m / s

$$m / s^2$$

N s

N / s

Solution

Question 8

$$ 1 m/s^{2}$$

$$ 2 m/s^{2}$$

$$ 4 m/s^{2}$$

$$ 9.8 m/s^{2}$$

Solution

Question 9

Acceleration is defined as the rate of change of velocity.

Its SI unit is $$m/s^2$$.

Negative acceleration is called retardation

All the above.

Solution

Question 10

7 m/s

14 m/s

28 m/s

56 m/s

Solution

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