# Physics gr11 review (acceleration)

1. Sep 14, 2010

### justme_girl04

1. The problem statements, all variables and given/known data

1. a 100m long train accelerates uniformly from rest. If the front of the train passes a railway worker 150m down the track at a speed of 25m/s, what will be the speed of the last car as it passes the worker?

2. a hot air baloon is rising up with a constant velocity of 4m/s. As the balloon reaches a height of 4m above the ground the balloonist accidentally drops a can of pop over the edge of the basket. How long does it take the pop can to reach the ground?

3.a stone is dropped from the roof of a high building. a second stone is droped 1s later. How far apart are the stones when the second one reached the speed of 23m/s?

3. a rock is dropped from a seacliff and the sound of it stirking the ocean is heard 3s later. If the speed of sound is 330m/s, how high is the cliff?

2. Relevant equations
These are the equations we were given to solve the questions:
(it might look messy, f is final and t is time)
Vf=V1+at
d=V1+1/2at^2
d=Vft-1/2at^2
d=(V1+Vf/2)t

honestly i tried doing these, but i just dont get it!

Last edited: Sep 14, 2010
2. Sep 14, 2010

### nick850

1. 150/25 = 250/x
x = 41.6666667m/s

2. this one is weird. can't help. are you sure you copied all the data?

23^2=0+2(9.8)d
d=27 m (stone 1)

d = (vi+vf/2)t
27 = (0+ 27/2)t
t=2 seconds( the first stone reached 27m in two seconds)

2s -1s = 1s so we want to calculate the position of stone 2 at one seconds so

d = vi + .5at^2
d = 0 + .5*9.8*1^2
d = 4.9m

21 - 4.9 = 22.1m difference

4. 3s * 330m / 1s = 990 m

have no clue if any of these are correct. please check my work guys

3. Sep 15, 2010

### justme_girl04

Hey thanks for the help, the first and third make sense.. yea it know the second is weird but i read the question over and thats what it says. the 4th one is way off lol, it was a pretty long solution that came to a heights of h=4.9(2.9)^2