1- Chris jumps off a bridge with a bungee cord (a heavy stretchable cord) tied a
ID: 1543291 • Letter: 1
Question
1- Chris jumps off a bridge with a bungee cord (a heavy stretchable cord) tied around his ankle, (Figure 1) . He falls for 15 m before the bungee cord begins to stretch. Chris's mass is 75 kg and we assume the cord obeys Hooke's law, F=kx, with 54 N/m .If we neglect air resistance, estimate what distance d below the bridge Chris's foot will be before coming to a stop. Ignore the mass of the cord (not realistic, however) and treat Chris as a particle.
2- A 19.0-kg child descends a slide 1.80 m high and reaches the bottom with a speed of 1.50 m/s .
How much thermal energy due to friction was generated in this process?
3- A ski starts from rest and slides down a 28 incline 50 m long.
A- If the coefficient of friction is 0.090, what is the ski's speed at the base of the incline?
B- If the snow is level at the foot of the incline and has the same coefficient of friction, how far will the ski travel along the level? Use energy methods.
4- An 78-kg football player traveling 5.2 m/s is stopped in 1.0 s by a tackler.
What is the original kinetic energy of the player? What average power is required to stop him?
5- A 34.0-kg crate, starting from rest, is pulled across a floor with a constant horizontal force of 225 N. For the first 11.0 m the floor is frictionless, and for the next 10.0 m the coefficient of friction is 0.20. What is the final speed of the crate after being pulled these 21.0 m?
Explanation / Answer
1) figure is missing for this question.
2) m = 19 kg ; h = 1.8 m ; v = 1.5 m/s
The PE at top is:
PE = m g h = 19 x 9.8 x 1.8 = 335.16 J
KE at the bottom is:
KE = 1/2 m v^2 = 0.5 x 19 x 1.5^2 = 21.375 J
energy lost(thermal energy generated) due to friction would be:
E = PE - KE = 335.16 - 21.375 = 313.785 J
Hence, E = 313.785 J
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.