Physics education research, electronic materials, and the musings of Christopher Moore, Ph.D.
Physics education research, electronic materials, and the musings of Christopher Moore, Ph.D.
You are not logged in.
Qn:
During a thunderstorm, hail of diametre 1.0 cm falls directly downwards at a speed of 25 m/s.
There are estimated to be 125 hailstones per cubic metre of air.
a) What is the mass of each of hailstone (density = 0.92 g/cm^3)?
[ i got this one, don't know if its needed for the 2nd part ]
V = (4/3)(pi)(0.5 cm)^3 = (0.524 cm^3)(0.92 g/cm^3) = 0.48 g
b) Assuming that the hail does not bounce, find the magnitude of the average force on a flat roof measuring 10 m x 20 m due to the impact of the hail.
( Hint: During impact, the force on a hailstone from the roof is approximately equal to the net force on the hailstone, because the gravitational force on it is small. )
.. this is where I'm stuck
any help on how to do this part of the question would be appreciated = )
Thank You !
- mandy : )
Offline
I know you're probably way past needing the answer, but I might as well answer anyway.
Hailstone:
Mass = 0.00048 kg
Velocity = 25 m/s
Momentum = 0.012 kg-m/s
25 meters cubed of hailstones go past every second, so there are approximately 3,125 hailstones hitting 1 meter squared a second. From this we can deduce that there is 625,000 hailstones hitting the roof a second.
625,000 hailstones per second, so there is 300kg of mass on the roof from the hail on average, and that is 3000 Newtons of force.
Offline
