Answer
given,
mass of ice hockey player = 110 Kg
initial speed of the skate = 3 m/s
final speed of the skate = 0 m/s
distance of the center of mass, m = 30 cm = 0.3 m
a) Change in kinetic energy
b) Average force must he exerted on the railing
using work energy theorem
W = Δ KE
F .d = -495
F x 0.3 = -495
F = -1650 N
the average force exerted on the railing is equal to 1650 N.
Answer:
3 km/h
Explanation:
Let's call the rowing speed in still water x, in km/h.
Rowing speed in upstream is: x - 2 km/h
Rowing speed in downstream is: x + 2 km/h
It took a crew 9 h 36 min ( = 9 3/5 = 48/5) to row 8 km upstream and back again. Therefore:
8/(x - 2) + 8/(x + 2) = 48/5 (notice that: time = distance/speed)
Multiplying by x² - 2², which is equivalent to (x-2)*(x+2)
8*(x+2) + 8*(x-2) = (48/5)*(x² - 4)
Dividing by 8
(x+2) + (x-2) = (6/5)*(x² - 4)
2*x = (6/5)*x² - 24/5
0 = (6/5)*x² - 2*x - 24/5
Using quadratic formula
A negative result has no sense, therefore the rowing speed in still water was 3 km/h