A 50 kg pole vaulter falls from rest from a height of 5 meters onto a foam rubber pad. The pole vaulter comes to rest 0.22 seconds after landing on the pad. Calculate the athlete's velocity just before reaching the pad. Answer in m/s.
I am so confused about which formula to use with this problem. I tried doing it like this, but I don't know if it's right:
final velocity= initial velocity+(gravity)x(time)
final velocity= 0m/s + (-10m/s)(0.22s)
This is a trick question.
The time it takes to decelerate to zero depends upon the spring constant of the foam material, and they give you no information about that, so you cannot get the answer by using the decleration time. You have to get of from the height that he falls from, as follows
V = sqrt (2 g H) = 9.9 m/s
V(f)^2=v(i)^2 + 2a(y)
So
V(f)^2=0 + 2(9.8)(5)
V(f)^2=100
V(f)≈10 m/s
Your attempt to solve the problem is on the right track, but there are a few things that need clarification.
First, you correctly recognized that the acceleration due to gravity is -10 m/s^2. The negative sign indicates that gravity acts downward.
To calculate the final velocity, you can use the formula: final velocity = initial velocity + (acceleration)(time).
However, you need to determine the initial velocity. The given information states that the pole vaulter falls from rest, which means the initial velocity is 0 m/s.
So, using the formula: final velocity = 0 m/s + (-10 m/s^2)(0.22 s), you can now calculate the answer.
final velocity = 0 + (-10)(0.22) = -2.2 m/s
The negative sign indicates that the velocity is directed downward, which makes sense because the pole vaulter falls towards the foam rubber pad.
Therefore, the athlete's velocity just before reaching the pad is -2.2 m/s.