Originally Posted by

**Coach** Hello!

**Ok, I am just a beginner so sorry if I am wrong but hopefully I can type out the main bulk and then some more experianced people can confirm it. Sorry...**

I have three physics questions.

1) if I have a velocity time graph, and the acceleration is not constant how can I calculate the displacement when the velocity is $\displaystyle 35ms^-1 $

**I'm guessing it is a polygon. Just find the area of the space beneath the line, by splitting it up into different sections, this will equal the distance travelled (the displacement.)**

If it is a curve, you will have to draw in your own polygon.

(I doubt it is a curve though because it would of just asked for an aproximation unless you are doing higher level where you would need to use more advanced maths.)

2) A ball is dropped and let fall for 6 seconds until it crashes through a glass plate. In this crash it loses two thirds of its velocity. After the crash it takes the ball 2 s to reach the ground. How high from the ground is the glass plate?

**v = acceleration due to gravity (in this case) = 9.8**

s = displacement = ?

t = time = 6

u = 0

s = (u+v)/2 x t

4.9 x 6 = 29.4

3) How can I calculate the amount of days it takes for water with Radon with activity of 10 000 Bq/l to 1000 Bq/l, if the half-life of Radon is 3.8 days?

**10 000, 5000, 2500, 1250, 625**

I think the answer is 3.8 x 4 = 15.2 days

This is for it to get to 625 though, maybe I have done this wrong though, haven't done it since gcse modulers.

I feel hopeless. I don't know how to do these and the physics test is tomorrow. If someone could help me I would be really grateful.

Thank you!