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Answer:
(a)
(b)
Explanation:
According to the law of conservation of momentum:
Initially, the girl and the plank are at rest. So, relative to the ice, we have:
(a) The velocity of the girl relative to the ice is:
Here, is the velocity of the girl relative to the plank and
is the velocity of the plank relative to the ice.
Replacing (1) in (2):
(b) According to (2), the velocity of the plank relative to the surface of ice is:
The negative sing indicates that the plank is moving to the left.
Given Information:
Energy of laser pulses = E = 100 mJ = 100×10⁻³ Joules
Time = t = 1 ns = 1×10⁻⁹ seconds
Required Information:
Instantaneous power = P = ?
Answer:
Explanation:
The instantaneous power is the power dissipated at any instant of time whereas the average power is the power dissipated over a given time interval.
The instantaneous laser power during each pulse is given by
Where E is the energy of the laser pulses and t is the time that each pulse lasts.
or
Therefore, the instantaneous power of each pulse is 100 Mwatt.