A hockey player has an acceleration of 3.1 m/s2. How long does it take him to come to a complete stop from a speed of 13 m/s?

a)16.1s
b) 4.2s
c)0.24s
d)9.9s

Question

A hockey player has an acceleration of 3.1 m/s2. How long does it take him to come to a complete stop from a speed of 13 m/s? 

a)16.1s 
b) 4.2s 
c)0.24s 
d)9.9s

anonymous · Answer

Use the kinematic equation for motion:

$$v_f = v_0+at$$v_f represents your final velocity which should be zero since he stops at that point and you are given an initial acceleration (your "a") and an initial velocity (your v_0) now solve for "t" which is the time it took to reach 0 velocity

anonymous · Answer

so would it be set up: 
0=13+ (3.1)(t) ?

anonymous · Answer

Yes. However, you're going to get a negative "t", but if we want a positive "t" or time we need to set that acceleration as negative as it is decelerating to reach a 0 velocity, but we don't need to go in depth for this kind of problem. 

solve for "t" now and you can get your answer. =)

anonymous · Answer

so, how would you solve for (t) if it is in the equation when it equals to 0?

anonymous · Answer

Well, you have a regular 13 by it self and then you got 3.1 multiplied to "t" and the whole thing equals to 0

Why can't I subtract 13 from each side to bring it to the other side? so it doesn't equal to 0 anymore. It's the same thing right? 

$$0= 13 + 3.1t$$subtract 13 from each side$$-13=3.1t$$you can solve it from here right?