Solving Projectile Motion Problems: Tips and Help for Beginners

[sens_freak_18]

Please any form of help would be great! Me and two friends tried to solve these problems today and we tried for more then an hour and still did not get the correct answers. I'm not asking that you just flat out give me the answers but just help me through it and give me some tips on how to solve it so that i know what I'm doing.

1)If an object with a horizontal velocity of 3.5 m/s rolls off a cliff 13.0 m above ground find:

a) the total time the object is in the air ( for this we got 1.6 but i think it is incorrect)

b)the range the object travels ( for this one we got 5.6 m, still think this is incorrect)

c) the final velocity( both magnitude and direction) (we got 15.9 m/s[down])

2) Jumping at an angle of 45 degrees to the horizontal a police officer in pursuit of a criminal leaps from the top of one building to another that is 4.5 m across and 1.0 m higher.

a)at what velocity will he have to leap to land on top of the next building?
b)how long is he in the air for?

For that one i have no clue where to start we have no velocity so I'm completely lost, I'm just asking for some help and just getting me started so i can complete the question.

Thanks a lot!

 

[cdhotfire]

For one separate it into vertical and horizontal components. That should help you out.

 

[cdhotfire]

The first one seems wrong and when you get the time wrong, then everything else goes kaboom.

 

[sens_freak_18]

For one separate it into vertical and horizontal components. That should help you out. Oh don't worry I've done that, it doesn't help.

The first one seems wrong and when you get the time wrong, then everything else goes kaboom. Yeah i figured that out too, it messes everything up!

 

[cdhotfire]

You should have
H | 0 m/s^2 | 3.5 m/s | ?
-------------------------------
V | -9.81 m/s ^2 | 0 m/s | 3 m

and because u have 3 terms in vertical you can find time.

 

[sens_freak_18]

what about number two, I'm really confused on that one, i just can't figure out where to start.

 

[cdhotfire]

id try to do #2 but I don't have time, it takes a while to do it at least my method, but ill get u started. There might be an easier way but make vertical Vi= tan 45 v, v equals the velocity.