We are given with:
Sensitivity: 100uJ/cm2
Diameter: 10mm
Background Optical Power: 8uW
Source Optical Power: 50uW
Required: exposure time
Solution:
Exposure time = sensitivity x area / (background power - source power)
= 100uJ/cm2 (π/4) (1 cm)² / (80 uW - 50 uW)
= 2.62 s
The exposure time is 2.62 seconds.
Answer:
the weight of astronauts on earth is greater than his weight on d moon
Explanation:
due to the greater gravitational pull in earth the weight seems to me more
but for the moon where there is less gravity
its weight will be less causing slight flotation
Answer:
P = W / t = m g s / t = m g v where work by auto = m g s
30 kw = 30000 watts = 30000 J / s
Work wasted = F v as shown above relating work and power
Work done against incline = m g s sin 8.75 and power against incline
= m g v sin 8.75 = 1222 v Joules / sec
power in moving auto = power available - power lost to friction
power in moving auto = 30000 - resistance = 30000 - 910 v
1222 v = 30000 - 910 v
v = 30000 / 2132 = 14 m/s
Note: constant resistance to motion must mean P = W / t = F s / t = F v