# How fast does a diver hit the water when jumping off a 30m platform?

• Medgirl314
In summary, the diver jumps off a platform 30 meters in the air and hits the water with a speed of 24.2 meters per second.
Medgirl314

## Homework Statement

A diver steps off a platform 30m above the water. With what speed does he hit the water?

v=intial v+at

## The Attempt at a Solution

I reached an answer of 2.47 seconds, but I can't see how I got there anymore! Is this answer correct?

Thank you very much!

Hi Medgirl314!

You need to learn the standard constant acceleration equations.

In this case, you know vi and a and s, and you want vf

so the equation to use is … ?

I think I used several equations, but they faded a bit. Blasted erasable pens. Since it's a fairly new concept, my physics teacher doesn't want me to have them memorized yet. I think I used y=y0+v0+1/2 at^2 and t^2=2y/a .

The answer seems plausible. Did I get it right?

Thanks again, and thanks for the link!

(try using the X2 and X2 buttons just

Hi Medgirl314!

(try using the X2 and X2 buttons just above the Reply box )
Medgirl314 said:
… my physics teacher doesn't want me to have them memorized yet.

rubbish!

there's only 3 basic equations, memorise them and everything will be much simpler!
I think I used y=y0+v0+1/2 at^2 and t^2=2y/a .

you mean y=y0+v0t + 1/2 at2

(and the second one is just another version of the first one, with zero constants)
The answer seems plausible. Did I get it right?

on this forum, you need to show your calculations, not just the answer

Oh! I'm sorry! My answer was actually 24.2 m/s. I gave you a different part that I used to find that answer. I think I used t=√2y/a, and got t=√2.3 m/9.8 m/s^2, giving a time of 2.47 seconds. Then I used v=vo+at , plugging in my numbers to get v=0+9.8 m/s^2(2.42 s), and then got my answer of v=24.2 m/s. Is this better? Thank you!

HI Medgirl314!

(never use . for multiplication … use x or * or brackets )
Medgirl314 said:
… I used t=√2y/a, and got t=√2.3 m/9.8 m/s^2, giving a time of 2.47 seconds. Then I used v=vo+at , plugging in my numbers to get v=0+9.8 m/s^2(2.42 s), and then got my answer of v=24.2 m/s. Is this better? Thank you!

yes, that's correct (you meant 30 not 3)

but quicker would have been to use vf2 = vi2 + 2as

Thank you! I must have used a dot for multiplication on my paper and didn't notice that it was 30, not 3.0!

## What is the formula for calculating the velocity of a falling object?

The formula for calculating the velocity of a falling object is v = gt, where v is velocity in meters per second (m/s), g is the acceleration due to gravity (9.8 m/s^2), and t is time in seconds.

## How does air resistance affect the motion of a falling object?

Air resistance, also known as drag, is a force that opposes the motion of a falling object. As an object falls, it experiences an upward force from air resistance that increases as its velocity increases. This can cause the object to reach a terminal velocity, where the upward force of air resistance equals the downward force of gravity, and the object stops accelerating.

## What is the difference between weight and mass?

Weight is a measure of the force of gravity on an object, while mass is a measure of the amount of matter in an object. Mass is typically measured in kilograms (kg), while weight is measured in newtons (N).

## How does the height of a falling object affect its velocity?

The height of a falling object does not affect its velocity. As long as the object is in free fall, its velocity will increase by 9.8 m/s every second, regardless of its starting height.

## What is the difference between free fall and controlled fall?

Free fall refers to the motion of an object under the sole influence of gravity, with no other forces acting on it. Controlled fall, on the other hand, involves an object being influenced by other forces such as air resistance or a person controlling its descent.

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