Question
A hockey player is standing on his skates on a frozen pond when an opposing player, moving with a uniform speed of 12 m/s, skates by with the puck. After 2.0 s, the first player makes up his mind to chase his opponent. If he accelerates uniformly at 4.0 m/s2, determine each of the following.
(a) How long does it take him to catch his opponent?(b) How far has he traveled in that time?
(a) How long does it take him to catch his opponent?(b) How far has he traveled in that time?
Answers
a. d1 = Vo*t + at^2,
d2 = 12(t+2),
d1 = d2,
0 + 0.5*4t^2 = 12(t+2),
2t^2 = 12t + 24,
2t^2 - 12t - 24 = 0,
Divide both sides by 2:
t^2 - 6t - 12 = 0.
Use Quadratic Formula to find t:
t = 7.58s.
b. d = 0 + 0.5*4*(7.58)^2 = 114.9s.
d2 = 12(t+2),
d1 = d2,
0 + 0.5*4t^2 = 12(t+2),
2t^2 = 12t + 24,
2t^2 - 12t - 24 = 0,
Divide both sides by 2:
t^2 - 6t - 12 = 0.
Use Quadratic Formula to find t:
t = 7.58s.
b. d = 0 + 0.5*4*(7.58)^2 = 114.9s.