A person has a mass of 80 kg. They go for a run with a constant speed of 3.5 m/s. When running against a resistive wind force they have to generate 50 W more power than running with the same wind force. How strong is the force due to the wind?
2006-11-17 06:12:17 · 2 answers · asked by flori 4 in Science & Mathematics ➔ Physics
If you run x1 meters against wind, the work you produce is A1=F*x1+f*x1; F is the force of your muscles to overcome the resistance of air with no wind, f is the force of the wind in your face. Let x1 be covered in time t1, then P1=A1/t1 is your power against the wind.
If you run x2 meters with the wind, the work you produce is A2=F*x2-f*x2; F & f being the same.
Let x2 be covered in time t2, then P2=A2/t2 is your power with the wind. They say that dP=P1-P2=50W or dP=(F+f)*(x1/t1)-(F-f)*(x2/t2). As x1/t1=x2/t2=v, then dP=2*f*v. Thus f=dP/(2*v)=50/7=7.14N is the force of the wind, m=80kg is excessive datum!
2006-11-17 08:53:33 · answer #1 · answered by Anonymous · 0⤊ 0⤋
50 times more than the normal wind force.
2006-11-17 14:17:11 · answer #2 · answered by neera k 1 · 0⤊ 0⤋