# Pole Vaulting Kinematics Problem

• physicsnobrain
In summary, the pole-vaulter leaves the ground with an upward speed of 9.5 m/s and reaches a height of 2.0 m above the launch point. The time required to reach this height is 0.2 seconds. However, there are two possible answers for this question due to the fact that the pole-vaulter must come down after going up. Depending on the kinematic equation used, one may get both solutions or just one.

## Homework Statement

A pole-vaulter leaves the ground with an upward speed of 9.5 m/s.
(a) How fast is she going when she is 2.0 m above the launch point?
(b) How long is required to reach this height?
(c) Why are there two answers to (b)?

## The Attempt at a Solution

Question A and B I don't have a problem with. I worked out A to be 7.1 m/s (2 sig digs) and B to be 0.2 seconds (2 sig digs).

However it is question C I am not understanding. I feel tempted to write "because I can write the answer in seconds or I can write it in minutes". But I feel this is a silly answer, therefore I need help.

physicsnobrain said:
However it is question C I am not understanding. I feel tempted to write "because I can write the answer in seconds or I can write it in minutes". But I feel this is a silly answer, therefore I need help.
When the pole vaulter goes up, she must come down.

CAF123 said:
When the pole vaulter goes up, she must come down.

So there could be one answer that measures her going up and one answer that measures her going up then coming down?

physicsnobrain said:
So there could be one answer that measures her going up and one answer that measures her going up then coming down?
Yes, depending on what kinematic equation you use you will either get the two solutions automatically or not.