A bird flying at a height of 12 m doubles its speed as it descends to a height of 6.0 m. The kinetic energy has changed by a fac
1 answer:
Answer:
Option d)
Explanation:
As the Kinetic energy of the body ids due to the speed of the body and depends on it, it does not depend on the height of the body.
The kinetic energy is given by:
KE =
where
m = mass of the body
v = kinetic energy of the body
Now, as per the question:
Initial velocity is u
and final velocity, v = 2u
Thus
Initial KE = (1)
FInal KE = =
FInal KE = 4 (2)
Thus from eqn (1) and (2):
Final KE = 4(Initial KE)
The Kinetic Energy has changed by a factor of 4
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Answer:
1. False 2) greater than. 3) less than 4) less than
Explanation:
1)
- As the collision is perfectly elastic, kinetic energy must be conserved.
- The expression for the final velocity of the mass m₁, for a perfectly elastic collision, is as follows:
- As it can be seen, as m₁ ≠ m₂, v₁f ≠ 0.
2)
- As total momentum must be conserved, we can see that as m₂ > m₁, from the equation above the final momentum of m₁ has an opposite sign to the initial one, so the momentum of m₂ must be greater than the initial momentum of m₁, to keep both sides of the equation balanced.
3)
- The maximum energy stored in the in the spring is given by the following expression:
- where A = maximum compression of the spring.
- This energy is always the sum of the elastic potential energy and the kinetic energy of the mass (in absence of friction).
- When the spring is in a relaxed state, the speed of the mass is maximum, so, its kinetic energy is maximum too.
- Just prior to compress the spring, this kinetic energy is the kinetic energy of m₂, immediately after the collision.
- As total kinetic energy must be conserved, the following condition must be met:
- So, it is clear that KE₂f < KE₁₀
- Therefore, the maximum energy stored in the spring is less than the initial energy in m₁.
4)
- As explained above, if total kinetic energy must be conserved:
- So as kinetic energy is always positive, KEf₂ < KE₁₀.
To solve this problem we will use the trigonometric concepts to find the distance h, which will allow us to find the speed of Jeff and that will finally be the variable that will indicate the total tension, since it is the variable of the centrifugal Force given in the vine at the lowest poing of the swing.
From the image:
When Jeff reaches his lowest point his potential energy is converted to kinetic energy
Tension in the string at the lowest point is sum of weight of Jeff and the his centripetal force
Therefore the tension in the vine at the lowest point of the swing is 842.49N
