edexcel maths m1 question?

mayesford

mayesford

mayesford

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i was hopeing someone could help me with this question i have to do for homework, which is from a text book, so i do have the answer, but it is difficult.
Question - Particle A of mass 1kg is at rest 0.2m from the edge of a smooth horizontal 0.8m high table. It is connected by a light inextensible string of length 0.7m to a partcle B of mass 0.5kg. Partcle B is intially at rest at the edge of the table closest to A but then falls off. Assuming B's initial horizontal velocity to be zero find the speed with which A begins to move?

thank you
 
I presume that you have drawn a diagram?

The first thing you will notice is that the string becomes taught when B has fallen 0.5m.

Simply equate potential energy of B to kinetic energy of A as the string is taught, so:

mgh = ke

and hopefully you should get the answer.

If you need any more help, feel free to ask ;)
 
MORE SPEED said:
I presume that you have drawn a diagram?

The first thing you will notice is that the string becomes taught when B has fallen 0.5m.

Simply equate potential energy of B to kinetic energy of A as the string is taught, so:

mgh = ke

and hopefully you should get the answer.

If you need any more help, feel free to ask ;)
Click to expand...
That would work if you were in a physics exam but you can't talk about energy in M1.
It's just a suvat question, V^2=U^2+2as.
 
Thanks for your reply's , but I was wondering if can you show me the working out, and in terms of Physics i have no knowledge of potential/kinetic energy, but if it is simple suvat question which I am more familiar with, wat would the acceleration be. Thanks. Also I have some more questions but I'll post tommoro , I'll take one question at a time.
 
mayesford said:
Thanks for your reply's , but I was wondering if can you show me the working out, and in terms of Physics i have no knowledge of potential/kinetic energy, but if it is simple suvat question which I am more familiar with, wat would the acceleration be. Thanks. Also I have some more questions but I'll post tommoro , I'll take one question at a time.
Click to expand...

Acceleration will just be g ( 9.8 m s ^2)
 
The initial speed, U, is 0.

The final speed, V, is the unknown that we want to solve.

The distance travelled by the particle, S, before the string becomes taught is 0.5m.

The acceleration, A, is the acceleration due to mavity, 9.8ms^-2.

Whack them into the equation and you get the answer.
 
Thank you very much to both of you, for the help, and "I will be back". I have about 4 more questions but I'll post them tommoro ,im going asleep know ,have to go school tommoro. Cheers
 
Please keep your maths problems to the same thread.

Also, people are not going to just solve it for you, you will need to explain what you want help with / what part you don't get.
 
mayesford said:
The answer I got from the suvat equation was 3.13, but the answer in the text book was 1.04
Click to expand...

Conservation of momentum. Momentum before A starts moving must equal momentum after A starts moving.

m_b * u = (m_a + m_b) * v

(1/2) * u = (0.5 + 1) * v

(1/2) * u = 1.5 * v

(1/3) * u = v

1.04... = v
 
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