Soru
A person jumps from the roof of a house 3.8-m high When he strikes the ground below, he bends his knees so that his torso decelerates over an approximate distance of 0.73 m Part A Part B If the mass of his forso (excluding legs) is 42 kg , find the magnitude of the average force exerted on his torso by his legs during deceleration Express your answer using two significant figures. F=
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Şahin
Elit · 8 yıl öğretmeni
Uzman doğrulaması
Cevap
To find the magnitude of the average force exerted on the torso by the legs during deceleration, we can use the equation of motion:
where:-
is the final velocity (0 m/s since he comes to rest),-
is the initial velocity,-
is the acceleration (deceleration in this case),-
is the distance over which the deceleration occurs.First, we need to find the initial velocity
when he starts to decelerate. We can use the equation:
Rearranging for
:
Given:-
m/s (final velocity),-
(acceleration due to gravity, negative because it's deceleration),-
m (distance of deceleration).Substituting the values:
Now, we can find the magnitude of the average force exerted on the torso by the legs during deceleration using the equation:
where:-
(mass of the torso),-
(acceleration due to gravity, negative because it's deceleration).Substituting the values:
Therefore, the magnitude of the average force exerted on the torso by the legs during deceleration is approximately
(rounded to two significant figures).