Question

what is (1/2)mv^2 = mgh ?? where this come from?

Answer 1

hi

Answer 2

(1/2)mv^2 is the definition of kinetic energy
mgh is the definition of gravitational potential energy

Answer 3

Try this http://www.wolframalpha.com/input/?i=1%2F2%29mv%5E2+%3D+mgh

Answer 4

Does that help?

Answer 5

i was trying to solve a physics problem, but then someone posted a solution starting with this equation (1/2)mv^2 = mgh

Answer 6

box with given mass is projected up and he used this.

Answer 7

can you type the question?

Answer 8

A block of mass M is projected up a frictionless inclined plane with a speed VO. The angle of incline is given as theta.

Answer 9

How am I supposed to know which equation to use..?

Answer 10

like someone used (1/2)mv^2 = mgh?

Answer 11

when you say projected, you you mean it was fired up an incline?

Answer 12

yes

Answer 13

ok so basically reason why I was confused with that equation is theres no such equation (1/2)mv^2 = mgh in my text book.

Answer 14

that's because there wouldn't be.

Answer 15

this equation is equating kinetic energy with potential energy

Answer 16

hmm

Answer 17

okok I will work on it!

Answer 18

what you have to understand though is that if there is an external force acting on the system, then you can ADD potential and kinetic energy;

Answer 19

if you are working within an isolated system, then energy must be conserved.
have you learned about conservation of energy?

Answer 20

Yes I do

Answer 21

hi @douglaswinslowcooper could you help me a bit?
I'm not sure how much to talk about

Answer 22

This meant that the kinetic energy gained (1/2)m v^2 came from the potential energy lost m g h.

Answer 23

This equation was from the Newton's Law subject

Answer 24

ok and building on what @douglaswinslowcooper just said
you lose potential energy, but it is converted into kinetic energy
you do not however see this as an equation in the book because it is expected that you learn that energy is conserved

Answer 25

oh i see

Answer 26

I'm cleared now

Answer 27

For an object falling due to gravity,
the sum of potential and kinetic energy remain constant

(1/2)mv^2 + m g h.

If you define g as <0 or>0 you will have a + or - problem to pay attention to

Answer 28

Ok I will work on it
thank you so much