Homework help pleaseeeee! :(

Gahhh I'm having trouble!

1.) If humans originated in Africa and migrated to other parts of the world, some time would be required for this to occur. At the modest rate of a mere one kilometer per year, how many centuries would it take for humans originating in Africa to migrate to China, some 10,000 kiliometers away?

2.) If you throw a ball straight upward at a speed of 10 m/s, how long will it take to reach zero speed? How long will it take to return to its starting point? How fast will it be going when it returns to its starting point?

3.) Calculate the hang time of an athlete who jumps a vertical distance of 0.75 meter.

4.) If a salmon swims straight upward in the water fast enough to break through the surface at a speed of 5 meters per second, how high can it jump above water?

Please help me only if you know what you're doing.

Thanks guys.

 

Well, just off the top of my head, 10000Km at 1Km/year = 10000 years = 100 centuries.

 

if we told you the answers...isn't that considered cheating?

 

this may help with the ball part,,,terminal velocity...the fastest possible rate a object will fall...ps only helping LOL

http://www.google.com/search?hl=en&q=terminal+velocity&spell=1

this link to calculation page

http://www.grc.nasa.gov/WWW/K-12/airplane/termv.html

LOL GLENN "S PAGE

 

Okay, ball throwing, I can help with that

you know s = uv+ 1/2at^2?

s = displacement,
u = initial velocity
v = final velocity
a = acelleration
t = time

your initial velocity is 10ms^-1
your final velocity is 0 (for the purposes of the first part of the question)
displacement, you don't know
acelleration is -9.81ms^-1 (gravity)
time you don't know, and you're trying to find out.

does that help at all?

 

Not necessarily.

 

Not really. I don't know what kind of math you're in... but I'm still in Algebra lol.

 

if i tell you what the answer is, then i helped you cheat.

nevermind.

 

I'm not cheating. I just need help. Chill out.

 

Ace we don't have to give the answers to be helpfull,,LOL,maybe just the logic behind them to help kickstart the motor???...I could have broken out the old sicentific calculator and gave the answer,,but insted I gave a equasion,,to be worked from,,Glenn

 

I take physics, so this thread is interesting (and helpful).

 

Oops, i got the equasion wrong

Code:

          1
s = ut + ---at^2
          2

And glenn - we don't know the drag of the "ball", and i highly doubt that after being thrown at 10m/s up in the air that the ball will reach terminal velocity, as to bring a football to terminal velocity you need to drop it from a rather large building

http://www.timallen.org/suvat.html

 

LOL goldie ,,,iM A NEW YORKER,,WE LIKE TALL BUILDINGS,,,HEHEHEHE,,,SO CALLED DROP A PENNY FROM THE eMPIOR sTATE bUILDING lol...JUST THOUGHT THE MATH CONCEPT, could be helpfull,,,,,,,opps sorry for caps just looked up .HUMMMM.and think it looks cool so I will leave it LMAO