How does mass come into play in this problem?

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SUMMARY

The discussion focuses on the physics of a soldier falling from a helicopter and the resulting impact on snow, specifically analyzing the net acceleration and direction of that acceleration. The soldier, weighing 180 lb (approximately 81.65 kg), falls from a height of 150 ft (approximately 45.72 m) and creates a 4.1 m crater upon impact. Participants clarify that while mass influences gravitational force (m*g), it does not affect the calculation of acceleration during free fall or impact, as acceleration can be determined using initial and final velocities alone.

PREREQUISITES
  • Understanding of Newton's laws of motion
  • Familiarity with kinematic equations
  • Knowledge of unit conversion to MKS (meter-kilogram-second) units
  • Basic concepts of forces, including normal force and gravitational force
NEXT STEPS
  • Study kinematic equations for uniformly accelerated motion
  • Learn about gravitational force and its impact on free fall
  • Explore the concept of impulse and momentum in collision scenarios
  • Investigate the effects of different surface materials on impact dynamics
USEFUL FOR

This discussion is beneficial for physics students, educators, and anyone interested in understanding the principles of motion, impact dynamics, and the role of mass in physical calculations.

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Where / how does mass come into the following problem?

A 180 [lb] soldier has an accident: He fell down from a helicopter hovering at 150 [ft] above a snow packed ground. The impact of his body created a 4.1 [meter] crater in the snow. Convert all units into MKS units and find:

a) His net acceleration in the snow [m/s^2] (assume constant)
b) the direction of this net acceleration


If I treat the soldier as just an object in free fall from the time he falls from the helicopter until the time he hits the ground I can find his final velocity just before hitting the ground. Knowing the depth of the crater and the velocity just before hitting the snow and at the bottom of the crater (zero) I thought that I could find his acceleration, but I do not see how mass comes into play here...When he hits the snow m*g will be greater than the normal force but he comes to a stop so the Fn and m*g are equal then...

Any thoughts / ideas would welcomed.
 
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Since, as you point out, you have (or can figure out) the initial and final speed, you can find the acceleration. Mass is not needed for that calculation.
 
Thank you for the clarification.
 

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