Ryan wrote:
Half those formulas you guys gave me aren't even on my sheet. No wonder I can't figure any of them out, they don't give any example problems in the textbook, I basically have to figure it out with formulas I haven't even been taught.
Here's some of the problems I have:
1. What is the displacement of a truck accelerating from 10m/s to 20m/s in 5.0s?
2. If a cyclist travelling at 14.0m/s skids yo a stop in 5.60s, determine the skidding distance.
3. A train's stopping distance is 1.3km. If the train was at an initial velocity of 90km/h, determine it's accelration during braking.
4. A rocket starts from rest and accelerates uniformly for 2.00s over and displacement of 150m (w). Determine the acceleration.
5. A jet starting from rest reaches a speed of 241km/h on 96.0m of runway. Determine the acceleration.
If you could provide me the formuals, I can solve it. It's just I can't find any formulas that will give me the right answer.
You have to change the formulae around. So, for question 5:
Q5
You have been given: initial velocity (0 because it says 'from rest'), final velocity (241), displacement (96m)
You need to find: acceleration
Formula that fits the bill: V^2 = U^2 + 2AS
So now re-arrange the formula to get acceleration on its own:
V^2 = U^2 + 2AS
2AS = V^2 - U^2
2A = (V^2 - U^2) / S
A = ((V^2 - U^2) / S) / 2
And now let's fill it in:
A = ((241^2 - 0^2) / 96) / 2
A = ((58081 - 0) / 96) / 2
A = (58081 / 96) / 2
A = 605 / 2
A = 302.5m^2 (acceleration is always in squared!)
And then to check to make sure you got the right answer:
V^2 = U^2 + 2AS
58081 = 0 + (2 x 302.5^2 x 96)
58081 = 2 x 29040
58081 = 58080 (missed out by 1 because of rounding)
Got it?