Find the initial acceleration of block B

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Homework Help Overview

The problem involves a block B of negligible mass connected to a 1 kg mass via a non-stretchable string. The scenario describes the initial conditions where the 1 kg mass is given a horizontal velocity while the system is at rest, and the goal is to determine the initial acceleration of block B.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the implications of the negligible mass of block B and the tension in the string, with some asserting that this leads to an acceleration of g for block A and suggesting that block B should also accelerate to the right. Others question the validity of the given answer of 2g and explore the need for a diagram to clarify the situation after the particle has moved.

Discussion Status

The discussion is ongoing, with various interpretations being explored regarding the forces acting on the blocks and the initial conditions of the system. Some participants have suggested that the 1 kg block must be held in place by an external force, while others express skepticism about the provided answer of 2g, indicating a lack of consensus on the correct approach.

Contextual Notes

There are indications that the problem may involve assumptions about the setup, such as the positioning of the 1 kg block and the effects of gravity being ignored in certain interpretations. Participants are also considering the implications of the system being initially at rest.

Vivek098
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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.
 

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Vivek098 said:

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?
 
Please see the attachment.
 
Vivek098 said:
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.
 
PeroK said:
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.
 
Vivek098 said:
The acceleration is zero since there are no forces.

Are you sure? That means the block won't move?
 
PeroK said:
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?
 
Abhishek kumar said:
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.
 
PeroK said:
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
 
  • #10
PeroK said:
The answer of 2g looks wrong to me.
Agreed. Should more than double that.
PeroK said:
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.
 
  • #11
haruspex said:
Or just instantaneously at rest, the two blocks having previously been propelled leftwards and upwards respectively.

Slightly trickier for a lab technician to arrange!
 

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