Time Projectile Problem Solved - Thanks!

[MrRandom66]

Problem solved, many thanks

 

[grzz]

Write down some equations that may be used. The we can discuss which of them can apply.

 

[obafgkmrns]

You might want to check your units.

 

[MrRandom66]

I'm really not sure what equations to use. I have a list of some equations but they ask for the initial velocity.

 

[grzz]

You can find the initial speed in the vertical direction.

 

[MrRandom66]

You can find the initial speed in the vertical direction.

Could you explain that please?

 

[grzz]

Try to find what is known in the vertical direction.

 

[MrRandom66]

Try to find what is known in the vertical direction.

Vertical displacement is 15m, and Gravity due to acceleration is 9.8 m s^2

 

[grzz]

initial speed
final speed
distance travelled
acceleration
time
Which of the above are known in the vertical direction?

 

[grzz]

What is the speed in the vertical at the maximum height?

 

[MrRandom66]

Distance Travelled, and Acceleration?

Feel like I'm missing something here...

 

[grzz]

Vertical displacement is 15m, and Gravity due to acceleration is 9.8 m s^2

Correct but acceleration is negative if we choose upward direction as positive.

 

[MrRandom66]

Oh zero. I was missing something

 

[grzz]

Now you CAN find the initial speed in the vertical direction.

 

[MrRandom66]

Before I calculate the final speed, I have to get t, correct? So, am I write in believing this is 15m/-9.8 m s^2

 

[grzz]

Before I calculate the final speed, I have to get t, correct?

I think that you mean the initial (vertical) speed.

 

[MrRandom66]

I think that you mean the initial (vertical) speed.

Yes, I did.

 

[grzz]

If you know the initial and final vertical speeds, and the vertical distance you can find the time which is the quantity that you originally wanted to find.

 

[MrRandom66]

If you know the initial and final vertical speeds, and the vertical distance you can find the time which is the quantity that you originally wanted to find.

Sorry, I'm having a hard time getting my head round this.
I'm not sure what equation to use to find final velocity.

 

[grzz]

You will only learn how to do physics only if you try to pick the equation yourself.
Try to find - from notes or internet - the equations you can use.

 

[MrRandom66]

OK, I've got the equation for final velocity, give me a minute and i'll work out the time.

 

[MrRandom66]

Ok, so now I have the time, am I right in believe the total time for the projectile will be the time I've just calculated, x2?

 

[grzz]

Yes.

 

[MrRandom66]

Brilliant! Thanks, Now I've got to work out the launch speed... :-/

I'm going to double check my notes, but I'm sure i'll need help sooner or later.