1) extra problem sheet #11 ( apologies to Neel)
An 80 kg skater and a 40 kg skater face each other on slippery ice. Without digging in ( i.e. no friction) they push of each other. If the 80 kg skater has a velocity of 3 m/s north what is the 40 kg skater’s velocity?. If the 80 kg skater digs his skates in and pushes horizontally against the ice with a force of 100 to the north for 1.0 seconds while the second skater pushes against him exactly as she did in part (a) what will the 80 skater’s velocity be?
a) 40 kg skater has equla but opposite p so has a v= 6 m/s south
b) impulse from skater A on B = p' from part a= 80 x 3 north now the ice provides a J of 100N x 1 sec to the south so total J on B = 240 north =100 south = 140 pods north so v' in case b = 140/80 m/s = 1.75 m/s north
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