Change in Momentum = mv - mu.
u = 0, v = 10 m/s. Note ball accelerated from rest, so initial velocity = 0. u =0
Change in Momentum = mv - mu = 3*10 - 3*0 =30.
Change in Momentum = 30 kgm/s.
The watch hand covers an angular displacement of 2π radians in 60 seconds.
ω = 2π/60
ω = 0.1 rad/s
v = ωr
v = 0.1 x 0.08
v = 8 x 10⁻³ m/s
Answer:
2255 days
Explanation:
height, h = 1.8 km = 1800 m
amount of water, m = 3.2 x 10^7 kg
Power, P = 2.9 kW = 2900 W
Let t be the time taken
Energy required to lift the water,
E = m g h
E = 3.2 x 10^7 x 9.8 x 1800 = 5.65 x 10^11 J
Power, P = Energy / time
t = E / P = (5.65 x 10^11) / 2900
t = 1.95 x 10^8 second
t = 2255 days
thus, the time taken is 2255 days.
The old style (incandescent) light bulb converts more energy
into heat than it does into light. If you're using it mainly as a
source of light, then it's a bummer, and its efficiency is very low.
BUT ... if you're using an incandescent light bulb as a heater, then
its efficiency is much better. It all depends on your point of view.
