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(a)
The result of jumping from the second story balcony to the pavement below, landing stiff-legged on the feet.
(a)
Answer to Problem 1CQ
The person will incur injuries due to the large impulsive force acting on the person’s feet when he jumps from the second story balcony to the pavement below, landing stiff-legged on the feet.
Explanation of Solution
When a person is jumping from certain height, the possibilities of being injured internally depends primarily the average force acting to slow down the body. The impulsive force acting on the feet determines the likelihood of injuries.
The time interval for stopping for a person landing stiff legged on pavement is very short. Since the time interval is small, the average force acting on the person’s feet and other parts of leg is very large in accordance with the impulse-momentum theorem. The large impulsive force on the person’s feet and leg results the person to incur injuries when landing stiff legged on the pavement.
(b)
The result of a person jumping into a privet hedge, landing on his back and rolling to his feet.
(b)
Answer to Problem 1CQ
The likelihood of being injured upon jumping is very less when the person jumps into a privet hedge, landing on his back and rolling to his feet.
Explanation of Solution
When a person is jumping from certain height, the possibilities of being injured internally depends primarily the average force acting to slow down the body. The impulsive force acting on the feet determines the likelihood of injuries.
The time interval in stopping the person jumping into a privet hedge is high and as a result, the average force acting on the person’s torso is very low. Therefore, the likelihood of being injured upon jumping is very less when the person jumps into a privet hedge, landing on his back and rolling to his feet. However, the person may suffer superficial scratches.
(c)
The result of a person jumping into a firefighter’s net, landing on his back, and the method to increase the cushion the fall.
(c)
Answer to Problem 1CQ
The net stretches as the person falls into it, which increases the time interval in stopping the person. The person will not be injured during the event. In order to increase the cushion the person’s fall, the firefighter starts with the net held high and lower the net with their hands as the person lands.
Explanation of Solution
The firefighter’s net offers large time interval for bringing the person to rest. When the person falls in the net, the net stretches downward, gradually bringing the person to rest. The impulsive force in this situation is very low due to the large time interval.
In order to cushion the person’s fall, the firefighter starts with the net held high and lower the net with their hands as the person lands. This further extends the time interval during which the person is brought to rest.
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Physics
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