Kinetic and potential energy and speed

[crpcrpcrp]

is the initial velocity=0ms-1

 

[Hootenanny]

the potential energy=mass*gravity*height
=10*10*m
=100m

Correct! So since the object is at rest before it is dropped, all the energy is in the form of potential energy. So the constant in our equation must be...

 

[crpcrpcrp]

0?

 

[Hootenanny]

0?

If the total energy of the object must be constant then the total energy must be the same as the total energy at the start. Does that make sense?

 

[crpcrpcrp]

I understand

 

[Hootenanny]

Good, so now we have

2*potential energy = constant

2mgh = 20mh = 100m

20h = 100

Can you now go from here?

 

[crpcrpcrp]

i'm still a little confused. so what would be the constant?

 

[crpcrpcrp]

Good, so now we have

2*potential energy = constant

2mgh = 20mh = 100m

20h = 100

Can you now go from here?

what do i do form here?

 

[crpcrpcrp]

wait...
where did u get the 100?

 

[Hootenanny]

i'm still a little confused. so what would be the constant?

The constant would be the 100m as you stated yourself.

what do i do form here?

You should solve for h, the height of the ball when the potential energy is equal to the kinetic energy

wait...
where did u get the 100?

You derived it yourself;

the potential energy=mass*gravity*height
=10*10*m
=100m

 

[wisienkas]

at starting height you know that potential energy = constant

you know the constant is potential energy + kinetic energy.

therefore the potential energy and the kinetic energy is the same if 2*potential energy=constant

you can therefore say constant/2 = potential energy or constant/2= kinetic energy

since you get the potential energy from gravity*mass*height you can simply just isolate the height since you have te energy from the constant.

its more math than physics however. hope it helps for any looking in here