Why does sand feel hot under your feet on a sunny day at the beach?
2 answers:
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1) He has both potential and kinetic energy
2) Before the parachute opens, the potential energy decreases and the kinetic energy increases
Explanation:
1)
The gravitational potential energy of a body is the energy possessed by the object due to its position in a gravitational field, and it is given by:
where
m is the mass of the body
g is the acceleration of gravity
h is the height of the body above the ground
On the other hand, the kinetic energy of a body is the energy possessed by the body due to its motion; it is given by
where
v is the speed of the object
Here Mr. Leppold has both potential and kinetic energy before opening the parachute, because:
- It is moving at a certain speed, so , therefore he has kinetic energy
- He is at a certain height above the ground, , therefore he has potential energy
2)
The total mechanical energy of Mr.Leppold is the sum of the potential and the kinetic energy:
According to the law of conservation of energy, in absence of air resistance, this quantity remains constant.
During the fall, the height of Leppold decreases: this means that as decreases, the potential energy decreases too.
However, the total energy E must remain constant: therefore, this means that the kinetic energy KE must increase, and this occurs because the speed of Mr. Leppold increases as he falls.
Learn more about kinetic and potential energy:
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Answer:
The surface gravity g of the planet is 1/4 of the surface gravity on earth.
Explanation:
Surface gravity is given by the following formula:
So the gravity of both the earth and the planet is written in terms of their own radius, so we get:
The problem tells us the radius of the planet is twice that of the radius on earth, so:
If we substituted that into the gravity of the planet equation we would end up with the following formula:
Which yields:
So we can now compare the two gravities:
When simplifying the ratio we end up with:
So the gravity acceleration on the surface of the planet is 1/4 of that on the surface of Earth.