A projectile is launched straight up from ground level with an initial velocity of 320 ft/sec.
a) When will the projectile's height above the ground be 1536 ft?
b) When will the projectile hit the ground again?

Question

A projectile is launched straight up from ground level with an initial velocity of 320 ft/sec. 
a) When will the projectile's height above the ground be 1536 ft? 
b) When will the projectile hit the ground again?

anonymous · Answer

a)
$$ \frac{ 1536 ft }{ 320ft/s } $$
ft cancels out
$$ \frac{ 1536 }{ 320 s } $$
divide the numbers
$$4.8 s$$
The height will be above 1536 ft after 4.8 seconds

b) That seems to be a physics question, as no frictions or gravity was specified.