Find the initial acceleration of block B

[Vivek098]

Homework Statement

a block B of negligible mass is connected to a particle of mass 1 kg with a non-stretchable string. Now the hanging particle is given a velocity root(8gH) horizontally when system is at rest. Find the initial acceleration of block B.

Homework Equations

3. The Attempt at a Solution [/B]
Since Mass of Block is negligible, so Tension in String is Zero. Now for Block A, only force acting is mg in downward direction. So, acceleration of Block A is g in downward direction always. In the initial state, the acceleration of block A is equal to acceleration to Block B since they are directly connected by string. So, acceleration of Block B should be g towards right. But actual answer given is 2g.

 

[PeroK]

Homework Statement

a block B of negligible mass is connected to a particle of mass 1 kg with a non-stretchable string. Now the hanging particle is given a velocity root(8gH) horizontally when system is at rest. Find the initial acceleration of block B.

Homework Equations

3. The Attempt at a Solution [/B]
Since Mass of Block is negligible, so Tension in String is Zero. Now for Block A, only force acting is mg in downward direction. So, acceleration of Block A is g in downward direction always. In the initial state, the acceleration of block A is equal to acceleration to Block B since they are directly connected by string. So, acceleration of Block B should be g towards right. But actual answer given is 2g.

Try drawing a diagram of the situation after a short time. Hint: where are the two blocks?

 

[Vivek098]

Please see the attachment.

 

[PeroK]

Please see the attachment.

You need a diagram after the particle has moved somewhat!

Hint: assume the experiment is taking place on the horizontal. I.e. ignore the vertical force of gravity. What do you get then?

PS The answer of $2g$ looks wrong to me.

 

[Vivek098]

You need a diagram after the particle has moved somewhat!

Hint: assume the experiment is taking place on the horizontal. I.e. ignore the vertical force of gravity. What do you get then?

PS The answer of $2g$ looks wrong to me.

The acceleration is zero since there are no forces.

 

[PeroK]

The acceleration is zero since there are no forces.

Are you sure? That means the block won't move?

 

[Abhishek kumar]

Are you sure? That means the block won't move?

How could be system initially at rest as mentioned in question. How block b will hold the tension produce in string by 1 kg block?

 

[PeroK]

How could be system initially at rest as mentioned in question. How block b will hold the tension produce in string by 1 kg block?

The 1kg block must be held in place by some external force: it perhaps ought to have been shown at the edge of a small supporting platform.

 

[Abhishek kumar]

The 1kg block must be held in place by some external force: it perhaps ought to have been shown at the edge of a small supporting platform.

May be

 

[haruspex]

The answer of 2g looks wrong to me.

Agreed. Should more than double that.

The 1kg block must be held in place by some external force

Or just instantaneously at rest, the two blocks having previously been propelled leftwards and upwards respectively.

 

[PeroK]

Or just instantaneously at rest, the two blocks having previously been propelled leftwards and upwards respectively.

Slightly trickier for a lab technician to arrange!