A hunter shoots an arrow at a deer running directly away from him. When the arrow leaves the bow, the deer is at distance of 42 m. When the arrow strikes, the deer is at a distance of 51 m. The speed of the arrow is 68 m/s.

Question

A hunter shoots an arrow at a deer running directly away from him. When the arrow leaves the bow, the deer is at distance of 42 m. When the arrow strikes, the deer is at a distance of 51 m. The speed of the arrow is 68 m/s. 
What must have been the speed of the deer? (m/s) How long did the arrow take to travel to the deer? (s)

oobleck · Accepted Answer

how long does it take the arrow to travel the 51m? time = distance/speed = 51m / (68m/s) = 0.75s so, since speed = distance/time, the deer's speed was (51-42)m/0.75s = 12 m/s