How is a change in gravitational potential energy related to work done? (1 Viewer)

d-alarmclock

Active Member
Joined
May 9, 2013
Messages
233
Location
Hiding from the HSC
Gender
Female
HSC
2014
I've read countless notes on this, but still can't seem to put it in words. This is a syllabus dot point also, and I don't want to just leave it unattended and just simply accept the formula.

Thanks in advance!
 

Zeref

Stare into my eyes.
Joined
May 6, 2012
Messages
710
Gender
Male
HSC
2014
This is what I wrote:



I understood the student guide just fine.
 
Last edited:

iJimmy

not dead
Joined
Oct 2, 2013
Messages
1,594
Gender
Undisclosed
HSC
N/A
Potential Energy is energy that is "stored" which can be converted into other forms of energy.
Gravitational potential energy (GPE) is the energy of a mass due to its position within a gravitational field.
e.g. If a ball is placed atop a cliff, it will have the stored energy.
Keep in mind that GPE is equivalent to work done in moving something to a point.
W = Fs:
W is work done(J)
F is force applied(N)
s is displacement(m)
From this equation, we can say that, if we take the Earth's surface as the point of 0 GPE, we can find GPE using:
GPE = mgh
m is the mass of the object(kg)
g is the gravitational acceleration of Earth(9.8ms^−2)
h is the vertical distance between the object and the Earth's surface(m)
Note that this equation can work with other planets as well, obviously switching the value of 9.8ms^−2 to whatever the other planet's gravitational acceleration is.
 

QZP

Well-Known Member
Joined
Oct 7, 2013
Messages
839
Gender
Undisclosed
HSC
2014
Potential Energy is energy that is "stored" which can be converted into other forms of energy.
Gravitational potential energy (GPE) is the energy of a mass due to its position within a gravitational field.
e.g. If a ball is placed atop a cliff, it will have the stored energy.
Keep in mind that GPE is equivalent to work done in moving something to a point.
W = Fs:
W is work done(J)
F is force applied(N)
s is displacement(m)
From this equation, we can say that, if we take the Earth's surface as the point of 0 GPE, we can find GPE using:
GPE = mgh
m is the mass of the object(kg)
g is the gravitational acceleration of Earth(9.8ms^−2)
h is the vertical distance between the object and the Earth's surface(m)
Note that this equation can work with other planets as well, obviously switching the value of 9.8ms^−2 to whatever the other planet's gravitational acceleration is.
OP's question is basically what you have bolded. Does not help to say "keep in mind" without a logical validation of it (looks like its from a textbook anyway). Basically OP's question is "why is it that when I do work on an object against a gravitational field, that work is stored as gravitational potential energy?".
 

d-alarmclock

Active Member
Joined
May 9, 2013
Messages
233
Location
Hiding from the HSC
Gender
Female
HSC
2014
OP's question is basically what you have bolded. Does not help to say "keep in mind" without a logical validation of it (looks like its from a textbook anyway). Basically OP's question is "why is it that when I do work on an object against a gravitational field, that work is stored as gravitational potential energy?".
Yes, exactly. How do you put into words the relation between the two.
 

strawberrye

Premium Member
Joined
Aug 23, 2012
Messages
3,292
Location
Sydney
Gender
Female
HSC
2013
Uni Grad
2018
"why is it that when I do work on an object against a gravitational field, that work is stored as gravitational potential energy?".

Simply put, just remember this important rule-the law of conservation of energy-which essentially states that energy cannot be created nor destroyed, it can only be transformed from one form to another. Hence, all objects have stored potential energy when they are not moving, however, from Newton's first law, you would have learnt that all objects will remain stationary unless an unbalanced net external force acts upon that object, and hence that force is essentially what we termed as work done on an object to move if against a gravitational field. It is a bit like trying to swim upstream-you need to put energy to counteract the resistive force of the opposing water current. And essentially, as you move against the gravitational field and you stop at a particular point, the kinetic energy used to move that object to that point is transformed to gravitational potential energy due to the fundamental physics fact that energy is always conserved. Hope this helps a bit.
 

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top