one simple physics question? please?

Question

i know this is wrong since i am suppose to be figureing this out myself. but i really cant get this one.


A 1300-kg rocket has a net propulsion force of 50 kN (kiloNewtons). Over a short time period, it uniformly speeds up from an initial velocity of 35 m/s to a final velocity of 60 m/s. Assume that the mass of the rocket is constant during this time period and that the net force is along the direction of motion.


i just need to find out how much time (in sec) it would take for the rocket to go from 35 to 60 m/s???

ahh thanks.. that seems soo simple.. really appreciate it.

Answer 1

acceleration = force/mass (a = F/m)

In this case, the force is 50000N and the mass is 1300 kg. So the acceleration is 50000/1300 = 38.46 meter/sec/sec.

Change in velocity = acceleration x time

The change is 60 - 35 = 25 meter/sec. So the time it would take is 25/38.46 = 0.65 seconds

Answer 2

okay my knowledge of physics is pretty rusty, but...

calculate the acceleration by using f = ma, so a = f/m (the 50,000 over the 1300)

now you have the acceleration, you can use
a = (v-u)/t (i think)

such that
t = (v-u) / a
so
t = (60-35) / a (which you found earlier)

hope this helps.

Answer 3

the of Newton's second law says

f=ma
soo a=f/m

and the definition of acceleration is

a=(V2-V1)/(t2-t1)

then
f/m=(V2-V1)/(t2-t1)

since t1=0 and t2 is the time of acceleration we have

t2= (60-35)*1300/50000

mg=50kN=50000N

P.A.

Answer 4

Sorry i don't no but it's a good i dea putting it on yahoo.
Ive got to try it.