Newton Mechanics

Question 1

What are the things we use to model to simplify situiaom

Answer 1

1) model everything as particles, means they have no size and all the force is at a single point

2) light = means no weight and has no effect, so like strings

3) inextensibke means it csn’t extend so it’s the same length at all times, so tension across is the same

4) smooth means no friction

Question 2

Reaction FIRCE

Answer 2

In maths always perpendicular

Question 3

Tension

Answer 3

Is force that prevents objects from owing away from each other , so outward and they PUKL

Question 4

Thrust

Answer 4

Is force which prevents objects from coming together

It can be found in a rod but not in a string or rope (because this wouldn’t be taught enough so like string become floppy)

Arrows inwards and push

Question 5

Equilibrium

Answer 5

Means resultant force 0 in every plane

And physics it means no reuskktsnt moment

Question 6

For tension questions etc

Answer 6

Draw the body as one and find all forces acting on it

Question 7

Remember using second law f =ma, f is the resultant force in that direction put that unknown first

Question 8

Yh so direction of accerlation, make that the first thing !

Question 9

Same concept if in vector form!, use variabel wjere you can

Question 10

Make sure you always draw the direction of acceleration so you don’t mess up which variable to put first

Answer 10

Bro

Question 11

I guess if it is a force I’m general that pushes something down , you don’t find resultant, because it’s separate?

Question 12

Just draw a graph for eveything and equate to area it’s easier man

Question 13

Why is the acceleration of connected objects the same under what assumption?

Answer 13

Under assumption that string is light and inextensibke !

Question 14

Can combine whole one it’s to one? What happens to tension

Answer 14

It dissapeaes, basically tension is an internal force so is not affected by anything

Question 15

To find tension in a connected system what to do first

Answer 15

First find acceleration

Now apply to the second law to find out tension
Check it works with the other mass too

Question 16

Remember rukes for compression (thrust) and type of object

Answer 16

Can only be string rope tension rest is thrust

Question 17

Okay make sure direction if accerlwtion is correct!

Answer 17

If arrow thenitd notminus! Thus getting wrongs

If you use same direction arrow then Yh minus

Question 18

So after deceleration if you get a NGETIVE TENSION FIRCE , what does this mean if it is a bar

Answer 18

It means you are pushing towards car so it’s a thrust!

Question 19

Why are the tensions in a pulley the same?

Answer 19

Because the pulleys are SMOOTJ, so tensions in the strings are the same

Question 20

Some Importsnt things about pulleys

Answer 20

Here if greater mass on one side, all the others will move in that direction, so that’s direction of acceleration

• the tension AROUND A PULLEY IS THE SAME, the ones on other pulleys are different. Only same because smooth
• if surface is smooth, no friction force!

Find three equations of motion and simultaneously solve

Question 21

Again importsnt about where the masses go

Answer 21

Even if BIG MASS IN THE MIDDKE

As long as one mass bigger hanging than other side, WHOLE SYSTEM GOES IN THIS DIRECTION !

Question 22

AND WHAT ABOUT ACCELERATION , is it the same?

Answer 22

Yh if it is caused by the same weight, then all three everything has the SAME ACCELERATION

Question 23

If it’s just two masses cinncecte by pulley, lit jus pulley in the middle and mass on each side

Question 24

Okay so for falling down pulley, why can’t you find time and why do you have ti find velocity

Answer 24

Basically time can only be found. Y a quadratic , and so it’s not possible to know for sure which time it was

But velocity is constant

So now basically if it goes 0.2 down it gonna go 0.2 up

And then once the other hits floor thr tension is now 0

So the rising mass resuktsnt firce is only g

So it will decelerate until it reaches 0 velocity and then go downwards again

Now at 0 velocity it means it will be highest height

So need to find the distance it rises from initial velocity (which is same as finak velocity of the other) and to 0

And add to two times 0.2

Giving 0.433