Help with physics question on falling objects?

Question

Any help on the process and formulas used for this problem?

A woman on a 90 ft tall bridge sees a raft below moving at a constant speed. She drops a stone trying to hit the raft when it's 6 m away. The stone hits the water 2 ft in front of the raft. How fast was the raft going?

Answer 1

free fall so u=0 and g=9.8m/s/s and distance travelled by the raft
=6m-2ft and 2 ft=2*12/40 m approximately
time taken for the stone to fall through 90'
90=1/2*32*t^2
t^2=180/32
t=(180/32)^1/2
distance moved by the raft in this time
=6-(2*12/40)m
speed of the raft
=(6-2*12/40)*(1/(180/32)^1/2) m/sec

Answer 2

this will not be probably the most effective strategy to resolve this, however here is how I'd do it. First, determine the pace the item is at while it starts the final 34.zero m of its fall: difference of X = one million/two (v preliminary + v last)t, so 34.0m = one million/two (v preliminary + v last) occasions one million.10s so sixty eight.0m/one million.10 s = v preliminary + v last. Now, keep in mind that the acceleration of gravity is nine.80m/s^two, so as a consequence v preliminary plus v last = v preliminary + v preliminary + nine.80m/s^two occasions one million.10s so sixty one.eight m/s = two(v preliminary) + 10.8m/s. so v preliminary = 25.five m/s NOW, return to the equation above, however now your preliminary v is opening from leisure (while item was once dropped) till it reaches the 25.5m/s (while it begins the final 34.0m of its fall) so difference of x = one million/two(zero.0m/s + 25.5m/s) occasions (25.5m/s divided by means of nine.8m/s^s) = 33.2m (this works since after we recognise the velocity it's at in the course of the autumn, 25.5m/s, we understand how lengthy a TIME it's been falling, since we all know the acceleration of gravity) So it had already fallen 33.two meters earlier than it acquired to that 34.zero meter portion of the autumn, so it was once dropped from 33.two + 34.zero = sixty seven.two meters peak.

Answer 3

I think you need to spend a little more time working on these problems and a little less time asking people to do the problems for you. Or ask your teacher/professor for help - that's their job, and they love doing it, and that way they get to see that you are working hard for your grade. Plus you learn more when you get help from a live person sitting next to you - they can work with you so you understand the concepts, instead of just feeding you answers.

Answer 4

I need to know the mass of the stone.