Is energy measured in joules
2 answers:
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Explanation:
a) The height of the ball h with respect to the reference line is
so its initial gravitational potential energy is
b) To find the speed of the ball at the reference point, let's use the conservation law of energy:
We know that the initial kinetic energy as well as its final gravitational potential energy
are zero so we can write the conservation law as
Note that the mass gets cancelled out and then we solve for the velocity v as
Answer:
A. when the mass has a displacement of zero
Explanation:
The velocity of a mass on a spring can be calculated by using the law of conservation of energy. In fact, the total energy of the mass-spring system is equal to the sum of the elastic potential energy (U) of the spring and the kinetic energy (K) of the mass:
where
k is the spring constant
x is the displacement of the mass with respect to the equilibrium position of the spring
m is the mass
v is the velocity of the mass
Since the total energy E must remain constant, we can notice the following:
- When the displacement is zero (x=0), the velocity must be maximum, because U=0 so K is maximum
- When the displacement is maximum, the velocity must be minimum (zero), because U is maximum and K=0
Based on these observations, we can conclude that the velocity of the mass is at its maximum value when the displacement is zero, so the correct option is A.