Mechanics - Elastic Collisions In 2 Dimensions Flashcards

1
Q

What is NEL

A

Newtons experimental law (Newtons law of restitution)
e X speed of approach = speed of separation

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2
Q

What do you know about the direction of the impulse?

A

It will be perpendicular to the surface

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3
Q

In 2D impacts what do you know is true?

A

Parallel to wall nothing will happen
Perpendicular to the wall things happen

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4
Q

What is the main thing with these 2D questions?

A

Splitting the speed into its components (cos and sin)
Then saying that perpendicular to the surface NEL applies

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5
Q

What is the angle of deflection?

A

The angle where if you continued drawing the line of original motion and between the new motion

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6
Q

What is a good way to find the angle of deflection?

A

Sing dot products

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7
Q

What do you do when the wall isn’t vertical o horizontal?
First answer why you need to do this?

A

You can’t split into horizontal or vertical components as i and j are parallel and perpendicular to the axis not the wall

You find a vector to model the wall of the impulse. Then state the perpendicular vector. You can then use vectors to split the original speeds into parallel and perpendicular to the wall

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8
Q

How may you find out the vectors that are parallel to and perpendicular to the wall?

A

The Qs may say the wall is parallel to y=x so (11) is the vector
You may be able to calculate the impulse to find a perpendicular vector
You may have to use other methods (Mixed exercise Q13)

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9
Q

What vector is perpendicular to (ab)
How can you check?

A

(-ba)
The dot product should equal 0

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10
Q

When working with oblique impacts what direction is the Impulse in?

A

Along the line of centers

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11
Q

What is the important bit of oblique impacts?

A

Perpendicular to the line of centers nothing will happen

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12
Q

What are the 2 things that you need to use in oblique impacts most questions?

A

Conservation of linear momentum (com)
NEL

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13
Q

How do you lay out an oblique impacts question?

A
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14
Q

How do you do oblique impact questions if the line of centers isn’t parallel or perpendicular?

A

Use the vector method

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15
Q

What is an useful thing to remember with the vector method?

A

You can use the simplified versions of the parallel and perpendicular vectors

Gjohfeigek

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