Calculating speed from distance and acceleration???

[Nomis07]

I'm taking part in a course with the Open University and I have been given an assignment, which includes a question asking me to calculate the speed of someone diving off a diving board.

 

The distance given is 4.6m and the acceleration due to gravity is 9.8 m s-2.

 

I'm totally lost and have no idea where to start in trying to calculate this. The context of the question is in relation to solving equations by changing an equation round.

 

If anyone can shine some light on this for me I would be forever grateful.

[5614]

So a man, who is initially at rest (i.e. u=0m/s where u is the initial speed), falls down 4.6m under gravity (a=9.8ms^-2), and you want to know the final speed.

 

Well there are two ways of doing it:

 

1) you could use kinematic equations.

 

2) you could use conservation of energy. The gravitational potential energy (mgh) is converted in to kinetic energy (½mv²). You can equate the two, i.e. say: mgh=½mv², and then rearrange for v=?.

 

There is another thread where someone is asking slightly different questions, but they also use kinematic equations to get the answer, so you might find some useful information there.

[Royston]

Just to add, it would help if you could briefly explain the technique you're supposed to be using i.e OU assignments usually state at the top of the question...'this question covers Chapter 1 of the book.' You'll lose marks if you answer a question using the conservation of energy, when it specifically asks you to solve the problem using kinematics.

[Nomis07]

Man thanks for such quick replies. I think I eventually got there, figners crossed anyway. Thanks again.

[5614]

You can post your solution and we can check it, if you would like.

[Royston]

You can post your solution and we can check it, if you would like.

 

If he/she does that, the assignment will be withdrawn if it's before the cut-off date. Sorry, I should of mentioned this earlier. I found somebody attempting this on the physics forums, guidance e.g which equations to use...but not complete solutions.

 

It seems Nomis07 is aware of this, hence he/she didn't post the solution.