Projectile Motion Question (1 Viewer)

[cutemouse]

Hi all,

I've been trying to do this question but I don't know if the answers are wrong or if I'm doing it wrong... I need help with just d, e and f. I posted the whole question as there are follow-through bits.

But here are the questions.

A rocket is fired with an initial velocity of 150m/s at an angle of 30 degrees to the horizontal off the edge of a cliff 50m high.

a) What is the rocket's maximum height? 286.99m
b) How long does it take to reach its maximum height? 7.65s
c) What is its maximum height above the base of the cliff? 336.99m
d) How long does the rocket take to reach the base of the cliff from its maximum height?
e) How long is the rocket in the air?
f) How far from the base of the cliff does the rocket land?

Also, another question...
A space station is positioned 850km from Earth.
a) Calculate acceleration due to the Earth's gravity in this space station.
b) What would a 75kg person weigh in the space station (I know how to do this, if I find (a), just posted for the sake of it).

Thanks alot if you can help me,

Jason

 

[tommykins]

回复: Projectile Motion Question

d) y = 336.99, solve for t in the formula y = -gt^2/2 + ut
e) time max height + 7.65s
f) total time of flight * 150cos30.

 

[cutemouse]

Thanks man, how did you get (f)?

Any chance you could have a look at my other question?

Thanks alot,

Jason =D

 

[tommykins]

f) formula is change in x = intital velocty of x*total time of flight as we ignore air resistance.

i can't be bothered doing a) at the moment, can't seem to think of what formula to use

 

[Js^-1]

F = ma
The force due to gravity is give by .
F = Gm₁m₂/d²
We assume that the only force acting on the spacestation is gravity.
The force experienced is due to gravity, therefore the acceleration experienced is also due to gravity.

m_meg = Gm_mem_earth/d²
.: g = Gm_earth/d²

hmm...I think you need to know the radius of the Earth for this one.
Sorry, I'll try and figure it out when i get home, I'm late for school.

 

[cutemouse]

Uhh, that makes no sense to me... What's all the <sub> and stuff?

F = ma
The force due to gravity is give by .
F = Gm₁m₂/d²
We assume that the only force acting on the spacestation is gravity.
The force experienced is due to gravity, therefore the acceleration experienced is also due to gravity.

m_meg = Gm_mem_earth/d²
.: g = Gm_earth/d²

hmm...I think you need to know the radius of the Earth for this one.
Sorry, I'll try and figure it out when i get home, I'm late for school.