All Questions
15
questions
1
vote
1
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29
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Describe the decrease in potential energy if two forces are acting on it one conservative which is greater than other applied by us in opposite dirn [closed]
So imagine this situation.
An object is experiencing two forces, one due to gravity in downward direction and other applied by us in upward direction such that our force is less than gravitational ...
- 13
1
vote
1
answer
49
views
Do expanding mass shells gain energy?
I've found an article which says in section 2
an expanding gravitational system of given mass gains energy
Does an expanding gravitational system or an expanding shell of a given mass gain energy as ...
- 2,462
-1
votes
4
answers
125
views
Initial velocity of a body when the distance travelled by it in the last second before reaching its maximum height is $5\ \textrm{m}$ [closed]
I stumbled upon this problem recently, and it has been haunting me for more than a day at this point. The question is as follows:-
When a ball is thrown up, it reaches a maximum height of $h$, ...
- 103
0
votes
1
answer
59
views
Dropping a ball with increasing masses and measuring the time until it no longer bounces
How could one theoretically explain that when one drops several balls with different masses from the hand, the bounces are less if the ball has larger mass and comes to rest after a shorter period of ...
1
vote
3
answers
112
views
Why can circular motion not be used to calculate kinetic energy of a person standing on Earth?
I did this question: In a sense we all have kinetic energy, even when we are standing still. The earth, with a radius of $6.37×10^6 \mathrm m$, rotates about its axis once a day. Ignoring the earth's ...
- 11
0
votes
2
answers
145
views
Why does a system with zero resultant moment turn after temporarily force-tilted?
Say a beam, 3m long from end to end, has a pivot placed at its centre of mass, at half its length i.e. 1.5m. Objects with weight 200N each are placed on both ends of the beam. The system is in ...
- 340
3
votes
1
answer
89
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At what height should I drop my kids from to prevent getting splashed? [duplicate]
Today as I was performing my morning biological ritual, "dropping the kids off at the pool" and what not, the cold kiss of Poseidon on my behind inspired an idea for an experiment. What is ...
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0
votes
0
answers
68
views
What is the net work done on two different systems?
Assume that we applied a force on an object so it moves at a constant speed upward, and we defined our system as the object only.
I was taught in my physics class that if we want to calculate the ...
- 31
1
vote
1
answer
93
views
Some questions regarding graviational potential energy and the concept of potential energy in general
Starting off, I first want to know the relation between work and potential energy.
$\Delta\mathbf U = - W $
How was this expression formulated?
Moving on,
My second doubt was in the derivation of the ...
- 82
0
votes
1
answer
52
views
How does work done to move an object scale with more/less gravity?
First let me say that Physics is not my area of expertise and my knowledge from school is pretty rusty, so I apologize in advance if I am asking a totally stupid thing or I have a mismatched ...
- 23
2
votes
2
answers
632
views
Where does the energy come from that holds an orbit in place?
I found several answers on this site about the question of where gravitational energy comes from, but they are always explained with two objects falling towards each other, something that can be done ...
- 123
0
votes
2
answers
163
views
Mechanical energy and fluids
Suppose we have two tanks connected by a tube with a tap in the middle. One tank is filled with water to a height of $h$ and the other is empty. The tap is then opened and the water 'levels itself'. I ...
- 27
0
votes
2
answers
109
views
Travel by Earth rotation [closed]
why we can't go outside the atmosphere and travel with earth rotation .. and can we travel in the opposite direction of atmosphere by the same speed of atmosphere it’s moving at about 1,000 miles an ...
- 11
9
votes
1
answer
614
views
Marvin the Martian vs. the Death Star: how much energy will they actually need to disintegrate the Earth?
According to a detailed analysis by Dave Typinski, Marvin the Martian’s Illudium Q-36 Explosive Space Modulator will require $1.711 \cdot 10^{32}~\text{J}$ to shatter the Earth into a gravitationally ...
- 360
2
votes
1
answer
2k
views
Escape velocity problem
I was given a problem at school:
How much Energy do we need to make a rocket of mass $m$ faster than the escape velocity so that it can travel in outer space?
Here's how I worked:
I know that the ...
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