Test: Acceleration - NEET MCQ

 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

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.

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 

Velocity is decreasing so, acceleration is negative. Velocity is positive so direction is positive.

Hence option (C) is correct.

We know that change in velocity / time is acceleration.

And dimension of acceleration is LT^-2

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

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 t₁ and then it decreases afterwards.

The object is moving in a positive direction at first and after time t₁ it moves in a negative direction.
remember But it's velocity is not same , it decreased from v_o to zero and then increases from 0 

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.

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.