What is the maximum kinetic energy and potential energy of a swinging pendulum?

  • Thread starter Thread starter tgpnlyt7095
  • Start date Start date
  • Tags Tags
    Energy
Click For Summary
The discussion revolves around calculating the maximum kinetic and potential energy of a swinging pendulum with a mass of 0.7 kg and a maximum speed of 2.0 m/s. The maximum kinetic energy is calculated using the formula Ek = 1/2mv², resulting in 1.4 J. For potential energy, the formula Ep = mgh is used, but the height (h) is unknown, leading to a challenge in completing the calculation. A participant notes that, according to the Law of Conservation of Energy, the maximum potential energy should equal the maximum kinetic energy. The conversation emphasizes the importance of showing work and understanding the principles behind the calculations.
tgpnlyt7095
Messages
31
Reaction score
0
Physics Question regarding Work ( calculations of kinetic energy & potential energy )

A Pendulum of mass 0.7kg is swinging . The maximum speed of the pendulum, where the
pendulum's position is at it's lowest, is 2.0ms-1. Calculate the maximum kinetic energy of
the pendulum and the maximum gravitational potential energy of the pendulum as it is at its greatest height.

ok, youre understood, sorry yea first time using this ;x

Relevant equations:
Ek ( Kinetic Energy ) = 1/2mv²
Ep ( Potential Energy ) = mgh

The Attempted Solution :

Ek = 1/2mv²
= 1/2 x 0.7 x 2²
= 1.4J

Ep = m x g x h
= ( 0.7 kg ) x 10m/s² ( i shall do a round-up ) x h ( unknown )

i was stucked here as i can't get the value of 'h' o.o
 
Last edited:
Physics news on Phys.org
Hi tgpnlyt7095 and welcome to PF. Please follow the rules of this forum and use the template when you seek help with homework. Show us the relevant equations and tell us what you tried and what you think about the problem. We just don't give answers away.
 
I'm not sure if my answer's correct, but I'd say the max. potential energy is the same as the max. kinetic energy because of the Law of the Conservation of Energy. ALL of the potential energy should be converted to kinetic energy, hence the max. kinetic energy = max. potential energy.
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

Similar threads

  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 21 ·
Replies
21
Views
2K
Replies
9
Views
2K
  • · Replies 31 ·
2
Replies
31
Views
4K
  • · Replies 3 ·
Replies
3
Views
963
Replies
4
Views
2K
  • · Replies 7 ·
Replies
7
Views
1K
Replies
2
Views
1K
  • · Replies 6 ·
Replies
6
Views
2K