Question

Help please, my physics teacher neglected to teach me hang time and I can't find any good results online.

Calculate the hang time of an athlete who jumps a vertical distance of 0.75 meters.

*Note that this is 8th grade introductory physics

Answer 1

Hang time is just the time he was in the air so we can use the kinematics formula \[d = v_i+1/2at^2\] where a = acceleration due to gravity which is 9.81 m/s^2

Answer 2

the initial velocity is 0, and d = 0.75, solve for t

Answer 3

@refrac532

Answer 4

So, rearrange the equation to solve for time?

Answer 5

Correct

Answer 6

Solve for \[d = 1/2at^2\] since initial velocity is 0

Answer 7

I should've used g instead of a, but it doesn't matter just note you're using gravity

Answer 8

Um, so my teacher says that 10 m/s^2 is the gravitational acceleration for Earth (yes, I know it's 9.8 m/s^2), so would the equation be\[0.75 = 5m/s^2t^2\]?

Answer 9

I'm sorry @Astrophysics , I'm still a little confused about how to isolate t

Answer 10

I like to do the algebra first then plug in the numbers, but it's cool if you plug in the numbers in this case it made it easier!

So we have \[\frac{ (0.75m) }{ 5 m/s^2 } = t^2\] we divide both sides by 5 m/s^2 to cancel out the 5 m/s on the right, any idea how to get rid of the square on the t?

Hint: \[\sqrt{x^2} = x\]

Answer 11

So it would be \[\sqrt{\frac{ 0.75m }{ 5m/s^2 }} = t\] right?

Answer 12

Exactly!

Answer 13

I got about 0.387 seconds. @Astrophysics

Answer 14

Since the question is in 2 sig digs, lets stick with 2! So 0.39 s :)

Answer 15

Okay, thanks a lot!

Answer 16

Np