Relative Velocity

Classical Mechanics Level 2

A lift is moving up with an acceleration of $2\text{ m/s}^2$ . A main in it throws a ball up with a velocity of $12\text{ m/s}$ with respect to himself. The ball comes back to the man in time $t$ . If the ball doesn't hit the roof of the lift, then find $t$ .

Take $g = 10\text{ m/s}^2$ .

None of these 3 seconds 1 second 2 seconds

1 solution

Swagat Panda
May 27, 2015

$\text{Let the lift's velocity be v. Now it is obvious that}\rightarrow$

$\text{Displacement of the ball= Displacement of the man}$

$\Rightarrow (v+12)t-\frac { 1 }{ 2 } gt^{ 2 }=vt+\frac { 1 }{ 2 } at^{ 2 } \text{where a is the acceleration of the lift.}$

$\Rightarrow (v+12-v)t=\frac { 1 }{ 2 } t^{ 2 }(a+g)\\ \Rightarrow 12t=6t^{ 2 }\\ \Rightarrow t=2 \text{ seconds}$

it's given in vmc supplementary , right?

A Former Brilliant Member - 4 years, 10 months ago

I did this from somewhere else, maybe it is also in the supplementary, I am not too sure.

Swagat Panda - 4 years, 10 months ago

don't you attend class regularly?

A Former Brilliant Member - 4 years, 10 months ago

I think sir discussed it in the class or something like that, I don't remember exactly, and I am not going to the class from the last few days because I was ill and I have to see the videos of previous classes. Did you not go to the class today?

Swagat Panda - 4 years, 10 months ago

no i went to the class , but i saw that you commented during the class - time , due to which i deduced that you missed the class. also which discussion are you talking about ?

A Former Brilliant Member - 4 years, 10 months ago

Oh, Okay. Are you on any social network because I feel a little awkward talking here in comments?

Swagat Panda - 4 years, 10 months ago

Relative Velocity

1 solution

0 pending reports