Ask Experts Questions for FREE Help !
Ask
    luisa_006's Avatar
    luisa_006 Posts: 1, Reputation: 1
    New Member
     
    #1

    Oct 21, 2007, 03:05 PM
    kinetic energy
    a 5kg rock is dropped from a height of 92m. What is the kinetic energy when the rock is 40m from the ground?

    I know that the formula is kinetic energy=1/2mv(squared)

    but I don't have the time so how would I find the speed, v?
    tickle's Avatar
    tickle Posts: 23,796, Reputation: 2674
    Expert
     
    #2

    Oct 21, 2007, 03:10 PM
    I don't have the time either, you will have to do it yourself in time for your homework assignment tomorrow.
    Capuchin's Avatar
    Capuchin Posts: 5,255, Reputation: 656
    Uber Member
     
    #3

    Oct 21, 2007, 03:26 PM
    You can do this in 2 ways, either realise that the loss in potential energy is identical to the gain in kinetic energy, or you can work out the end speed using a SUVAT equation and use the KE equation you have there.

    I would say the potential energy way is easier.

    Either way, you're going to need to put the work in.
    terryg752's Avatar
    terryg752 Posts: 197, Reputation: 4
    Junior Member
     
    #4

    Oct 22, 2007, 03:58 AM
    Potential energy at height h = mgh

    ( m = mass, g = force of gravity)

    Kinetic energy at height 92 = 0

    Hence loss of potential energy in falling = mg (92 - 40) = 52 mg

    Hence Kinetic energy = 52 mg

    1/2 mv^2 = 52mg

    v^2 = 104g

    Substitute value g to get the answer!

Not your question? Ask your question View similar questions

 

Question Tools Search this Question
Search this Question:

Advanced Search

Add your answer here.


Check out some similar questions!

Potential Energy- Bonding Energy [ 1 Answers ]

Question: The net potential energy between two ions (e.g. Na+ andCl-) can be Represented as follows: EN =EA+ER = -A/r +B/rn (a) Calculate the bonding energy E0 in terms of the A, B, and n ...

Kinetic energy [ 1 Answers ]

Does anyone know any good kinetic energy experiments? Thanks much valued:)

Work,kinetic energy [ 1 Answers ]

In the equation for work why do you multiply force times displacement distance could'nt you just multiply forcec times the time it took the object to cover the displacement distance?

Internal and Kinetic Energy. [ 5 Answers ]

1. The problem statement, all variables and given/known data A 14.0 kg block is dragged over a rough, horizontal surface by a 78.0 N force acting at 20.0 above the horizontal. The block is displaced 5.00 m, and the coefficient of kinetic friction is 0.300. (a) What is increase in internal...


View more questions Search