Motion in a Straight Line Test 3

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Motion in a Straight Line Test 3

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Weekly Quiz Competition

Question 1
1 / -0

A boy throws up a ball in a stationary lift and the ball returns to his hands in 10 s. Now if the lift starts moving up at a speed of 5 m/s. The time taken for a ball thrown straight up to return to his hands is:

A
more than 10 s

B
less than 10 s

C
insufficient information given

D
equal to 10 s

Solution

Lift moving with Uniform speed = 5m / s
Ball is thrown inside the lift
The uniform velocity of the lift does not affect the relative velocity of the ball with respect to the boy.
Relative velocity of ball = 49m/s
⇒ Relative acceleration = 9.8
Thus, u(relative) = velocity of bell
t = 2u_r/ g_r
= (2 × 49) / 9.8
⇒ t = 10s
so, the ball will still return in 10 secs
Question 2
1 / -0

The displacement of a particle along x-axis is given by x = 4 + 6t + 5t². Its acceleration at t = 2s

A
2 m/s²

B
10 m/s²

C
1000 m/s²

D
100 m/s²

Solution
Question 3
1 / -0

On acceleration-time graph, a horizontal line indicates:

A
zero displacement

B
zero acceleration

C
constant velocity

D
constant acceleration

Solution

The horizontal line on any graph indicates that its value is not changing with respect to changing time if we are taking time on the x-axis and taking any physical quantity such as velocity, speed, acceleration on the y-axis and if the graph shows straight horizontal line means its value remains same w.r.t time hence its value is constant.
Question 4
1 / -0

The position x of a particle varies with time (t) as x = 3t² – 2t³.The acceleration of the particle will be zero at time

A
1

B
3/2

C
0

D
1/2

Solution

We know that acceleration is the second derivative of change in displacement wrt time, hence we get a = 6 - 12t
When a = 0 = 6 -12t ;
We get t = ½
Question 5
1 / -0

What does this graph indicate about the motion of an object ?

A
Object is moving in negative direction with positive acceleration

B
Object is moving in negative direction with negative acceleration

C
Object is moving in positive direction with negative acceleration

D
Object is moving in positive direction with positive acceleration

Solution

Velocity is decreasing so, acceleration is negative. Velocity is positive so direction is positive.
Hence option (C) is correct.
Question 6
1 / -0

The dimensions of (change in velocity / time) is

A
[LT^-2]

B
[LT^-1]

C
[L/T^-1]

D
[L/T^-2]

Solution

We know that change in velocity / time is acceleration.
And dimension of acceleration is LT^-2
Question 7
1 / -0

The dimensions of instantaneous acceleration is:

A
[LT^-²]

B
[LT²]

C
[L/T^-1]

D
[LT^-1]

Solution

Instantaneous acceleration is rate of change of instantaneous velocity with time or velocity upon total time, hence we get its dimension is same as of acceleration i.e. LT^-2
Question 8
1 / -0

What does this graph indicate about the motion of an object?

A
Object is moving in positive direction with positive acceleration

B
Object is moving in negative direction with negative acceleration

C
Object is moving in positive direction with negative acceleration

D
An object is moving in positive direction till time t₁, and then turns back with the same

Solution

Through the given graph we get that:
Velocity is decreasing from a positive constant to some negative number with zero at t₁
Distance from the original point increases from zero to t₁and then it decreases afterwards.
The object is moving in a positive direction at first and after time t₁it moves in a negative direction.
Question 9
1 / -0

On acceleration-time graph the area under the curve equals the:

A
Meaningless

B
Change in velocity

C
Displacement

D
Change in acceleration

Solution

The area under an acceleration graph represents the change in velocity.
In other words, the area under the acceleration graph for a certain time interval is equal to the change in velocity during that time interval.
Question 10
1 / -0

If the signs of the velocity and acceleration of a particle are the same, the speed of the particle ______________.

A
Remains same

B
Increases

C
Decreases

D
Cannot conclude anything

Solution

In this question, it has been asked about the signs of velocity and acceleration not about the values of velocity and acceleration.
So, if both the entities have same the signs, then the speed of the object will increase.
If it is accelerating in the positive direction, the negative velocity is decreasing, and the object is slowing down.

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Re-Attempt Weekly Quiz Competition

Motion in a Straight Line Test 3

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Motion in a Straight Line Test 3

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SHARING IS CARING

Question 1

more than 10 s

less than 10 s

insufficient information given

equal to 10 s

Solution

Question 2

2 m/s2

10 m/s2

1000 m/s2

100 m/s2

Solution

Question 3

zero displacement

zero acceleration

constant velocity

constant acceleration

Solution

Question 4

1

3/2

0

1/2

Solution

Question 5

Object is moving in negative direction with positive acceleration

Object is moving in negative direction with negative acceleration

Object is moving in positive direction with negative acceleration

Object is moving in positive direction with positive acceleration

Solution

Question 6

[LT-2]

[LT-1]

[L/T-1]

[L/T-2]

Solution

Question 7

[LT-2]

[LT2]

[L/T-1]

[LT-1]

Solution

Question 8

Object is moving in positive direction with positive acceleration

Object is moving in negative direction with negative acceleration

Object is moving in positive direction with negative acceleration

An object is moving in positive direction till time t1, and then turns back with the same

Solution

Question 9

Meaningless

Change in velocity

Displacement

Change in acceleration

Solution

Question 10

Remains same

Increases

Decreases

Cannot conclude anything

Solution

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2 m/s²

10 m/s²

1000 m/s²

100 m/s²

[LT^-2]

[LT^-1]

[L/T^-1]

[L/T^-2]

[LT^-²]

[LT²]

[L/T^-1]

[LT^-1]

An object is moving in positive direction till time t₁, and then turns back with the same