1. In a motor vehicle crash, as a car crushes, it absorbs some of the force of the collision.
2 answers:
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a) 0.94 m
The work done by the snow to decelerate the paratrooper is equal to the change in kinetic energy of the man:
where:
is the force applied by the snow
d is the displacement of the man in the snow, so it is the depth of the snow that stopped him
m = 68 kg is the man's mass
v = 0 is the final speed of the man
u = 55 m/s is the initial speed of the man (when it touches the ground)
and where the negative sign in the work is due to the fact that the force exerted by the snow on the man (upward) is opposite to the displacement of the man (downward)
Solving the equation for d, we find:
b) -3740 kg m/s
The magnitude of the impulse exerted by the snow on the man is equal to the variation of momentum of the man:
where
m = 68 kg is the mass of the man
is the change in velocity of the man
Substituting,
The astronaut will move at 0.4 m/s in the opposite direction to the wrench
Explanation:
We can solve this problem by using the law of conservation of momentum. In fact, the total momentum of the astronaut-wrench system must be conserved before and after the launch.
Before the launch, the total momentum is zero, since the astronaut is at rest:
p = 0 (1)
After the launch, the total momentum is:
(2)
where :
m = 2 kg is the mass of the wrench
v = 10 m/s is the velocity of the wrench
M = 50 kg is the mass of the astronaut
V is the recoil velocity of the astronaut
Since momentum is conserved, we can write (1) = (2), and so we can solve for V:
And the negative sign means that the astronaut will move in the opposite direction to the wrench.
Learn more about conservation of momentum:
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