- #1
diegojco
- 24
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Suppose you have a teleski to climb a skiway of d=600m and θ=15º respect horizontal and μk=0.06 is kinetic friction coefficient in the cable. 80 skiers of 75kg (m=6000kg in total) each one wants to climb at the top at v=2.5m/s constant, What's the power that engine must provide in order to maintain this speed with that charge of skiers? Answer: 350KW
I have used: Wexternal forces=ΔEmechanic+ΔEthermic+ΔEchemical=0, where ΔEmechanic=(m*(vf)2/2)+m*g*(hf)-(m*(vo)2/2)-m*g*(ho)=m*g*(hf), since vf=vo y ho=0, and ΔEthermic=fk*d=μk*m*g*d*cos(θ), and ΔEchemical is engine's energy to get the power, then:
P=-dEchemical/dt
and -dEchemical/dt=dEmechanic/dt+dEthermic/dt, hence:
P=m*g*v*(sin(θ)+μk*cos(θ))
P=46.61KW
This is not the answer, why?, please guide me and tell me what's the mistake.
I have used: Wexternal forces=ΔEmechanic+ΔEthermic+ΔEchemical=0, where ΔEmechanic=(m*(vf)2/2)+m*g*(hf)-(m*(vo)2/2)-m*g*(ho)=m*g*(hf), since vf=vo y ho=0, and ΔEthermic=fk*d=μk*m*g*d*cos(θ), and ΔEchemical is engine's energy to get the power, then:
P=-dEchemical/dt
and -dEchemical/dt=dEmechanic/dt+dEthermic/dt, hence:
P=m*g*v*(sin(θ)+μk*cos(θ))
P=46.61KW
This is not the answer, why?, please guide me and tell me what's the mistake.