Answer
(a) The pavement does not cushion the fall very much and if you lend stiff-legged, the collision with the ground lasts for a short time. As a result, the average force exerted to decelerate you to a stop is relatively large and this can result in an injury.
(b) The hedge provides some cushioning which increases the length of time the collision lasts, thus reducing the average force. Also, rolling to your feet spreads out the places on the body where the force is applied, and increases the time of the collision, which reduces the average force on the body and reduces the risk of injury.
(c) The net stretches and increases the distance and time that the collision lasts, which reduces the average force. By landing on your back, the force is spread across the whole area of the back, which reduces the risk of injury.The firefighters bring the net down as you land in the net, which helps to reduce the average force even more.
Work Step by Step
(a) The pavement does not cushion the fall very much and if you lend stiff-legged, the collision with the ground lasts for a short time. As a result, the average force exerted to decelerate you to a stop is relatively large and this can result in an injury.
(b) The hedge provides some cushioning which increases the length of time the collision lasts, thus reducing the average force. Also, rolling to your feet spreads out the places on the body where the force is applied, and increases the time of the collision, which reduces the average force on the body and reduces the risk of injury.
(c) The net stretches and increases the distance and time that the collision lasts, which reduces the average force. By landing on your back, the force is spread across the whole area of the back, which reduces the risk of injury.The firefighters bring the net down as you land in the net, which helps to reduce the average force even more.
In summary, increasing the length of time of the collision decreases the average force exerted on the body, and reduces the risk of injury.
