# Approximate impact force upon landing with parachute

• BCHurricane89
In summary, a soldier jumping from a height of 1000ft (304.8m) with a total weight of 300lbs (136.078kg) and a constant velocity of 24ft/sec (7.3152m/s) will experience an impact force of approximately 1.99kN (1990 N or 450 lbs) when landing. The calculation was done using the momentum equation and an approximated impact time of 0.5 seconds. Further research or clarification may be needed to accurately reference this force.
BCHurricane89

## Homework Statement

So this isn't a homework question, just something my brother-in-law asked me. He is in the Army, and wanted to know an approximate landing force he would experience when he lands. After attempting the problem, and looking things over, I realized it may be harder than once thought.

So, he told me he jumps from 1000ft (304.8m), and its a static line jump, so the parachute opens the instant he jumps from the plane. The total weight of him plus gear will be 300lbs (136.078kg), and he will fall at a CONSTANT velocity of 24ft/sec (7.3152m/s). From here, it was easy to calculate the time it would take him to reach the ground (41.667sec).

## Homework Equations

Initially I tried calculating acceleration with dv/dt, then realized if he has a constant velocity, there would be no acceleration, and therefore my plan of simply using a F=m*a would not work.

## The Attempt at a Solution

From here, I then decided maybe it's more of a impulse-momentum type question as I would need to approximate an impact time, which he said maybe 0.5 seconds. Of course to make this easier, I will assuming he lands completely in the vertical, and not at an angle. Obviously his legs and body are going to be absorbing the force, and to calculate this doesn't appear to be straightforward.

I turned to the momentum equation p=m*v, and calculated his momentum being 995.379kgm/s. For the Impulse equation of F*t=m*dv or rearranging for F=(m*dv)/t. Using the approximated imapce time of 0.5 seconds, this give a force of 1.99kN. I have no idea what to reference this too, or if it is even a correct way of approaching the problem, so any help would be appreciated. Thanks!

1.99 kN = 1990 N = approx. 450 lbs. compared to a jump weight of 300 lbs.

## 1. What factors affect the impact force when landing with a parachute?

The impact force when landing with a parachute is influenced by several factors, including the weight and velocity of the object, the surface area of the parachute, and the height from which the object is dropped. The shape and design of the parachute can also affect the impact force.

## 2. How is the impact force calculated when landing with a parachute?

The impact force can be calculated using the formula F=ma, where F is the force, m is the mass of the object, and a is the acceleration. The acceleration is affected by the velocity and deceleration of the object as it makes contact with the ground, which can be estimated using the height and time of descent.

## 3. Can the impact force be reduced when landing with a parachute?

Yes, the impact force can be reduced by using a larger surface area parachute, which can slow down the descent and decrease the acceleration. Additionally, landing on a soft surface, such as sand or grass, can also help reduce the impact force.

## 4. Is there a safe limit for the impact force when landing with a parachute?

The impact force when landing with a parachute should ideally be below 10 g's (the force of gravity). However, the exact safe limit may vary depending on the individual and their physical condition. It is important to properly train and follow safety protocols when using a parachute to minimize the risk of injury.

## 5. How does the impact force when landing with a parachute compare to other activities?

The impact force when landing with a parachute can vary greatly depending on the factors mentioned above. In general, it is lower than the impact force experienced in activities such as car accidents or high-impact sports like football. However, it is still important to take precautions and properly train when using a parachute to avoid injury.

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