Answer:

Explanation:
Force 1 
Force 2 
Acceleration at stage 2 
Generally the weight of the Craft W is given as
W= upward force(thrust)
Therefore

Answer:
LAW 1 : For a given metal and frequency, the number of photoelectrons emitted is directly proportional to the intensity of the incident radiation.
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LAW 2: For a given metal, there exists a certain frequency below which the photoelectric emission does not take place. This frequency is called threshold frequency.
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LAW 3: For a frequency greater than the threshold frequency, the kinetic energy of photoelectrons is dependent upon frequency or wavelength but not on the intensity of light.
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LAW 4: Photoelectric emission is an instantaneous process. The time lag between incidence of radiations and emission of electron is 10^-9 seconds.
Explanation:
One of the equations for force is: Force = mass × acceleration.
The force and mass are given and so:
F=15N
m=10kg
By plugging in these values we obtain:


So the acceleration is a=1.5m/s^2
Answer: scenario b and scenario c uses most power
Explanation:
Scenario a:
Work=120J
Time=8 seconds
Power=work ➗ time
Power=120 ➗ 8
Power=15
Power=15 watts
Scenario b:
Work=160J
Time=8 seconds
Power=work ➗ time
Power=160 ➗ 8
Power=20
Power =20 watts
Scenario c:
Work=200J
Time=10 seconds
Power= work ➗ time
Power=200 ➗ 10
Power=20
Power=20 watts
Scenario b and scenario c uses most power
It is a seismograph that would be most useful.