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AS Physics projectile motion help please!!

Please show me how to answer this question
Also could anyone just explain the whole concept and formulaes for me because the AQA textbook is very wordy and I don't understand it!

Q. An object is projected horizontally at a speed of 16m/s into the sea from a cliff top of height 45m. Calculate:
- how long it takes to reach the sea
- how far it travels horizontally
- its impact velocity

Thanks!
Reply 1
Consider vertical motion and horizontal motion separately. Then use SUVAT equations.
Reply 2
Start with 2 equations, one for the vertical distance and one for the horizontal distance.

s(vertical) = ut + 1/2at^2, but u = 0 as its projected horizontally so s(vertical) = 1/2(9.8)(t^2)

s(horizontal) = ut + 1/2at^2, but there is no horizontal acceleration so simply s(horiz) = ut, where u = 16

Also, the horizontal component velocity never changes, i.e. it is always 16 as there is no acceleration. The vertical component will change because of acceleration due to gravity.

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