stuntmans free fall; physics day help?

Question by Daydreamer: stuntmans free fall; physics day help?
length of vertical fall: 14 meters
time to fall: 1.9 s
height of drop platform from ground:30 m
height of braking track from ground:5 m
your mass:60kg

what is your actual acceleration in m/s^2 when falling?

what was your velocity in m/s at the end of the free fall section?

what is the time it should take for the free fall drop of 14 m if the track were frictionless?

the change in height from the drop to the start of the braking track is 25 m. calculate the speed in m/s at the start of the braking track is all the potential energy is converted to kinetic energy.

calculate your momentum in kg(m/s) as you enter the stopping track?

your momentum after stopping is 0. the average time to stop the car is 1.25 seconds. use the concepts of impulse and momentum to find the average braking force in Newtons on you while stopping?

what is the approximate force factor you experience during the braking process?

Thanksss. also for the first question, how do you find acceleration without knowing the final velocity?

Best answer:

Answer by electron1
what is your actual acceleration in m/s^2 when falling?
Distance = ½ * a * t^2
14 = ½ * a * 1.9^2
Acceleration = 28 ÷ 1.9^2

what was your velocity in m/s at the end of the free fall section?
Velocity = acceleration * time = (28 ÷ 1.9^2) * 1.92

what is the time it should take for the free fall drop of 14 m if the track were frictionless?
Free fall acceleration = 9.8 m/s^2
14 = ½ * 9.8 * t^2

the change in height from the drop to the start of the braking track is 25 m. calculate the speed in m/s at the start of the braking track is all the potential energy is converted to kinetic energy.
KE = PE
½ * m * v^2 = m * g * h, divide both sides by ½ * m
v^2 = 2 * g * h
v = √(2 * g * 25) This is the magnitude of the velocity at the start of the braking track

calculate your momentum in kg(m/s) as you enter the stopping track?
momentum = mass * v = 60 * √(2 * g * 25)

your momentum after stopping is 0. the average time to stop the car is 1.25 seconds. use the concepts of impulse and momentum to find the average braking force in Newtons on you while stopping?
Force * time = mass * ∆ v
∆ v = √(2 * g * h)
Force * 1.25 = 60 * √(2 * 9.8 * 25)
Force = 60 * √(2 * 9.8 * 25) ÷ 1.25

what is the approximate force factor you experience during the braking process?
I believe that the force factor is the coefficient of friction = µ
Friction force = µ * m * g = µ * 60 * 9.8
Friction force =Force
µ * 60 * 9.8 = 60 * √(2 * 9.8 * 25) ÷ 1.25
Solve for µ

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