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# Hard physics question

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1. Can anyone help with this please:
A pebble is dropped from a height level with the end of a diving board above a lake. The velocity of the pebble immediately before it hits the surface of the water is 12m/s. Calculate the height of the diving board.

The only answer i can think of is 12 (Got that by getting time as 1 second)
but I don't think that's right.
2. (Original post by LittleBoxes)
Can anyone help with this please:
A pebble is dropped from a height level with the end of a diving board above a lake. The velocity of the pebble immediately before it hits the surface of the water is 12m/s. Calculate the height of the diving board.

The only answer i can think of is 12 (Got that by getting time as 1 second)
but I don't think that's right.
7.3m

use v^2 = u^2 + 2as

btw the answer will be different depending on your value of g. I used g = 9.81
3. first step a little diagram.
mark distance as x or s (whatever you are used to using)
a=9.81ms or -9.81ms depending on your diagram
u=0m/s v=12m/s

do a suvat

t is missing

so I think we use v^2=u^2+2as

you have to do a suvat, you have to have a little cheat sheet with you until you memorise all the equations of motion. You might be given them on the formula sheet.
4. Isn't it just v^2 = u^2 +2as.
Where v = 0's^-1
u = -12 ms^-1
a = -9.8ms^-1

Posted from TSR Mobile
5. (Original post by KINGYusuf)
7.3m

use v^2 = u^2 + 2as

btw the answer will be different depending on your value of g. I used g = 9.81
(Original post by KINGYusuf)
7.3m

use v^2 = u^2 + 2as

btw the answer will be different depending on your value of g. I used g = 9.81
(Original post by flux capacitor)
first step a little diagram.
mark distance as x or s (whatever you are used to using)
a=9.81ms or -9.81ms depending on your diagram
u=0m/s v=12m/s

do a suvat

t is missing

so I think we use v^2=u^2+2as

you have to do a suvat, you have to have a little cheat sheet with you until you memorise all the equations of motion. You might be given them on the formula sheet.
(Original post by RossB1702)
Isn't it just v^2 = u^2 +2as.
Where v = 0's^-1
u = -12 ms^-1
a = -9.8ms^-1

Posted from TSR Mobile
Yes, thanks so much, I get it now. Anyone know how to answer this:
A journalist is deciding whether to walk, cycle, or take the bus to get to work. There are two routes he could take.The shorter route is along a 3.5km path that only pedestrians and cyclists are allowed to use. The bus takes a longer route along a road. Estimate how long it would take the journalist to walk the pedestrian route.
I have no idea, why have they given only distance?
6. as it's an estimate question I think you need to know or give a good guess for the speed of a person walking. With this piece of info you can then work out the time. (5km/h)

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