A 30 N rock falls from a 40 m cliff. At what point during its fall are itspotential and kinetic energies equal?
Answers
Answer:
Both energies are equal when the rock has fallen 20 m or equivalently when it is at a height of 20 m.
Explanation:
Potential and Kinetic Energy
The gravitational potential energy is the energy an object has due to its height above the ground. The formula is
Where:
m = mass of the object
g = acceleration of gravity (9.8~m/s^2)
h = height
Note we can also use the object's weight W=mg into the formula:
The kinetic energy is the energy an object has due to its speed:
Where v is the object's speed.
Initially, the object has no kinetic energy because it's assumed at rest.
The W=30 N rock falls from a height of h=40 m, thus:
Since the sum of the kinetic and potential energies is constant:
U' + K' = 1,200 J
Here, U' and K' are the energies at any point of the motion. Since both must be the same:
U' = K' = 600 J
U'=Wh'=600
Solving for h':
Both energies are equal when the rock has fallen 20 m or equivalently when it is at a height of 20 m.
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As per the question the mass of the object is given as 70 kg.
The height of the object from ground is 8 m.
We are asked to calculate the potential energy of that object.
The potential energy of a object is the energy gained by the body due to its position or configuration. The energy due to the position of object from the surface is called gravitational potential energy .
If a body of mass m is at a height of h from the ground,then its potential energy is calculated as -
potential energy
where g is the acceleration due to gravity.
we have been given h= 8 m and m= 70 kg
we know that acceleration due to gravity g =9. 8 m/s^2
⇒
=5488 Joule
Here Joule is the unit of energy.
Answers
Answer:
dont know
Explanation:
need points
A) The pieces will repel because the cut end of the top magnet is not a magnetic pole.
B) The pieces will attract because the cut end of the top magnet is not a magnetic pole.
C) The pieces will repel because the cut end of the top magnet is a south pole.
D) The pieces will attract because the cut end of the top magnet is a north pole.
Answers
The answer to this problem is "OPTION C" i.e. The pieces will repel because the cut end of the top magnet is a south pole.
A magnet as a collection of tiny magnets, called magnetic domains. Each of these domain reinforces the magnetic fields of the other domains and hence the net magnetic field of magnet is generated. Each one of these domains have a tiny north and south pole. If you cut a magnet in half (along the line suggested in the problem), the newly cut faces will become the new north or south poles of the divided parts.
Answer:
c
Explanation:
Answers
The probability of (E and F) = P(e) times P(f) = 0.76 x 0.45 = 0.342 .
The probability of (e OR f) =
1 - P(not e AND not f) =
1 - P(not e) x P(not f) =
1 - (1 - 0.76) x (1 - 0.32) =
1 - ( 0.24 ) x ( 0.68 ) = 1 - 0.1632 = 0.8368.