Calculate: 5656

Janko is skating at a speed of 18 km/h. Its kinetic energy is 0.5 kJ. Janko weighs 40 kg.
1. what work will the braking forces do before Janko stops?
2. How big is the braking force when Janko stops after crossing a track of 14 m.?

Correct answer:

W =  0.5 kJ
F =  128.5714 N

Step-by-step explanation:

v=18 km/h v1=18/3.6=5 m/s m=40 kg E=0.5 m v12=0.5 40 52=500 J W=E/1000=500/1000=0.5 kJ
s=14 m s = vt/2 t=2 s/v1=2 14/5=528=5.6 s a=v/t=18/5.6=14453.2143 m/s2 F=m a=40 3.2143=128.5714 N

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