## Tuesday, 19 February 2013

### 1.9 describe the effects of forces between bodies such as changes in speed, shape or direction

Changes in speed
When an object is stationary it has an equal force pushing down and up. The downward force being gravity and the upward force being the surface the object is on. The object is not floating but it is not going into the ground.

When an object is accelerating it has the upwards and downwards forces but it also has forwards and backwards forces (drag and friction). The forward force is larger than the backward force when an object is accelerating.

When an object is going at a constant speed it has downward and upward forces as well as forward and backward forces. The forward and backward forces are equal, so the speed doesn't change even though the object is moving.

When an object is decelerating it has the equal upward and downward forces as well as forward and backward forces, but the backward force is larger than the forward one, slowing the object down.

Changes in shape
changes in shape affect momentum. Force= change in momentum/ time taken. An example of this is crumple zones in car decrease the force on the passengers.

Changes in direction
Which ever direction the force is greatest in will be the direction the object travels in.

1. what did you do for revision

1. I wrote out these blogs, and then I made posters on each point, and then I made flash cards! but I also did lots of past papers which was very helpful :)

2. THANK YOU!!!

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4. i still love you bae

5. NO PROBLEM Tiago!

1. Haha thank you Jenna, good luck in the exam :)

3. This is possibly the best thing I've ever discovered on the internet

1. I like to think so haha

2. Just kidding- thanks

5. what are the forward and backward forces

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2. thank u so much!!!this was very helpful.

3. Forward force can be momentum and/or thrust
Backward is drag and/or friction

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1. Thanks for your comment, I'm fairly sure they plagiarised me and am now getting in touch.

7. OMG thank you so much, these were so helpful, i got a mock exam coming up soon to go over the last term and this helped so much with my revision, thank you! :))

8. did you print off the past papers or can you buy them already printed?

1. I didn't print them, just looked at them online; if you can do this it saves time, money and the planet :) if not some schools will print them out and sell them as booklets but apart from that you mostly have to print yourself :P

9. So well explained :) Thank you so much

10. is it thrust or friction as the forwards force??

11. Extremely helpful Hannah, thank you.
By “forwards and backwards forces” and ‘drag and friction’ did you mean thrust and friction’ as drag is also a backwards force?
Thanks again :)

12. Thank you so much this really helps for my end of year exam

13. Thanks gal