By lucas posso romo
2

The best tip for any revision is to start with the past exam papers and work back from that. Otherwise you will spend a lot of time revising the wrong stuff, or the right stuff in the wrong way.
All past papers and mark schemes are available for free for you to download. You need to know your exam board and specification, but you can start here:-
Edexcel - http://qualifications.pearson.com/en/support/support-topics/exams/past-p...
OCR - http://www.ocr.org.uk/i-want-to/download-past-papers/
AQA - http://www.aqa.org.uk/exams-administration/exams-guidance/find-past-pape...

Tabitha Farrant

Also, find a million revision tips to make sure you spend your time effectively here
http://www.s-cool.co.uk/content/revision-secrets-no-end-insider-tips-psy...

Tabitha Farrant
By trust mambemba
1

Sorry if this is too complex, but it give you the idea.
Pacemaker cells in the sinoatrial node, located over the right atrium, initiate the cardiac cycle. Systole begins when excitation spreads over both atria, activating atrial contraction. Excitation spreads to the atrioventricular node, near the atrioventricular border, from which excitation is conducted by the bundle of His and the Purkinje system (groups of specialized muscle cells) to the bottom of the ventricles. Excitation spreads upward in the ventricles, contracting them from the bottom up, like squeezing a toothpaste tube from the bottom. When the action potentials end, diastole (relaxation) begins, until excitation is again initiated by the pacemaker cells of the sinoatrial node.

Tabitha Farrant

what is its speed after 8sec?
how long will it take to reach a speed of 36ms?

1

v = u+a.t
U= initial velocity = 0
So v = a.t
a=4, t=8. Pop in the numbers and get the answer
Rearrange v=a.t to get
t =v/a
Velocity required = V = 36. a=4
Pop in the numbers and get the answer
For distance you have to use s=ut + 0.5a.(t.t) (t.t) = t squared
initial velocity u=0 so ut = 0
Rearrange to get
t = ????
Pop the numbers in to get the answer
To get the speed after that time, use v = a.t again as per the start of the question
Finally to get distance (s) travelled in the 3rd second, find out the speed at the start (t=2) of that second using the techniques above. That will be u, initial velocity for this part of the question.
Then use s=ut + 0.5 a(t.t) to get the distance, s.

Tabitha Farrant
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