# Calculating Force of Hail Stones on a Roof

• binicle
In summary: Therefore, the force of the hail at time t is (2200 x .833) g. This is not the answer you are looking for. Try again.
binicle
I cannot know how to calculate the force of the hail
During a violent thunderstorm, hail the size of marbles (diameter = 1.20 cm) falls at a speed of 14.0 m/s. There are estimated to be 110.0 hailstones per cubic meter of air. Assume that, as for ice, 1.00 cm3 of hail has a mass of 0.920 g. What is the mass of each hailstone?
What is the magnitude of the force exerted by the hail on a 9.0 m x 20.0 m flat roof during the storm ? Ignore the bounce of the hail on impact.

Hi, binicle, welcome to the site!
What work have you done on this problem so far?
What values do you know?
What equations might be useful?

hi, i only calculated the mass of the hail,
1cm^3 has a mass of 0.920g
--> the hail has volume pi.d^3/6 = 0.905
--> the mass of hail is 1.017
Actually, i have no idea about how to calculate the force!
i think F = mg , but it is wrong.

Last edited:
binicle said:
hi, i only calculated the mass of the hail,
1cm^3 has a mass of 0.920g
--> the hail has volume pi.d^3/6 = 0.905
--> the mass of hail is 1.017
Actually, i have no idea about how to calculate the force!
i think F = mg , but it is wrong.

You might want to think more carefully about your mass calculation. It looks to me like that has units of g/cm^4. Hint: Mass would have units of grams.

F = ma, always. So once you have the mass right, see if you can figure out what the acceleration of the hail would be when it hits the roof.

Dorothy

i have just calculated again,
V = 0.905 cm^3
and mass = 0.905 x 0.920 = 0.833 g.
F = ma , but i don't know how to find acceleration of the hail? is it a = g =9.81 ?
Also, where will we use v=14 m/s and 9.0 m x 20.0 m flat roof and 110 hails in 1 m^3? I can not figure out anything related to those number.
Thank you.

NOTE: I do I know how to reach the final answer. But I think I can go one step further than what you have so far.
If there are 110 hailstones/m^3 of air, then every m^3 of air has a mass of (.833g/hailstone)(110hailstones/m^3 air). What to do next, I have no idea. You'd think a=-g, but the velocity obviously is important as well... What section of physics is this question testing you on?

binicle said:
i have just calculated again,
V = 0.905 cm^3
and mass = 0.905 x 0.920 = 0.833 g.
F = ma , but i don't know how to find acceleration of the hail? is it a = g =9.81 ?
Also, where will we use v=14 m/s and 9.0 m x 20.0 m flat roof and 110 hails in 1 m^3? I can not figure out anything related to those number.
Thank you.

The total force on the roof will be the sum of all the forces of all the hails that are hitting it at a given moment.

So you still need to calculate the force of one hail to do that.

If a car is traveling at 30 m/s, and two seconds later it is stopped, it had to accelerate to do that. Could you calculate the acceleration of the car? If it hit something that made it stop in two seconds, what force would it have exerted on the thing it hit?

Unfortunately, I have to log off now, but I hope this gives you enough to solve your problem. If not, maybe someone else will step into help.

Dorothy

actually, i don't know how many hail will exert on the roof, because 110 hails in 1m^3 doesn't say anything about the number of the hails.

It does, actually. Can you use work/kinetic energy to solve this? You never said where you were in your study of physics.

hi, I'm studing momentum & impulse,
i think the force exerted by the hail at time t is the force of the number of hails instantaneously exerting the roof at time t. Not all the hails in a volume V, just the hails in the surface.

## 1. How do you calculate the force of hail stones on a roof?

To calculate the force of hail stones on a roof, you can use the formula F = ma, where F is the force, m is the mass of the hail stone, and a is the acceleration due to gravity (9.8 m/s^2). First, determine the mass of the hail stone by measuring its weight in grams and converting it to kilograms. Then, multiply the mass by 9.8 to calculate the force in Newtons.

## 2. What factors affect the force of hail stones on a roof?

The force of hail stones on a roof can be affected by several factors, including the size and weight of the hail stones, the angle of impact, and the material and slope of the roof. The acceleration due to gravity (9.8 m/s^2) is constant and does not change the force of the hail stones.

## 3. How can I estimate the force of hail stones on a roof without measuring them?

If you do not have access to a scale to measure the weight of the hail stones, you can estimate their force by using the average weight for their size. For example, a small hail stone with a diameter of 1 cm typically weighs around 0.5 grams, while a large hail stone with a diameter of 5 cm can weigh up to 50 grams. You can use these averages to estimate the force using the formula F = ma.

## 4. Can the force of hail stones on a roof cause damage?

Yes, the force of hail stones on a roof can cause damage, especially if the hail stones are large and the roof is made of a less durable material. The force of the hail stones can cause dents, cracks, or even punctures in the roof, which can lead to leaks and other structural issues.

## 5. Is there a way to reduce the force of hail stones on a roof?

There are a few ways to reduce the force of hail stones on a roof. One option is to install a hail-resistant roof, which is made of materials that are more durable and can withstand the impact of hail stones. Another option is to add a layer of insulation or padding between the roof and the hail stones, which can absorb some of the force. Additionally, regularly maintaining and repairing any damage to the roof can help prevent further damage from hail stones.

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