Mechanics External L2 Forces

Front 1

Force

Back 1

A push or pull. Si unit N. A vector.

Front 2

F=ma

Back 2

Formula showing the relationship between mass of an object acceleration it'll experience under any given force.

Front 3

Net force

Back 3

The remaining fore after all forces acting upon an object have Ben added together to give one final force. This determines the change in motion of an object.

Front 4

Hooke's Law

Back 4

How springs will behave when loads are placed on them. Loads either stretching or compressing force. When stretched or compressed springs produce price known as restoring force, it tries to move the spring back to its origin.

Front 5

Used to calculate extension or compression of a spring

Back 5

Hooke's Law. Equation:

F= -kx

Front 6

What does spring constant describe?

Back 6

The stiffness of the spring. Large the spring, the harder to compress, ie. Car springs.

Front 7

The negative symbol in Hooke's Law equation?

Back 7

Indicates the force is in the opposite direction to the extension, the force trying to move the spring back to its equilibrium position. Becomes positive if extended rather than compressed.

Front 8

Newton's First Law

Back 8

An object maintains constant velocity incl. being stationary unless acted upon by an external net force.

Front 9

Newton's Second Law

Back 9

If an object experiences an external net force, it will accelerate such that Fnet=ma

Front 10

Newton's Third Law

Back 10

When an object exerts force on another, the second object will simultaneously exert a force the same size and opposite direction to the force acting upon it.

Action has an equal and opposite reaction.

Front 11

Forces acting at angles

Back 11

Make triangle's sides the force, acceleration etc. Exerted. Typically rearrange for F=ma.

Front 12

Centripetal Acceleration

Back 12

In circular motion, an object is constantly changing direction. Change of direction means velocity of object is changing, therefore object is undergoing acceleration. The objet accelerates even while maintaining a constant speed. Towards the centre acceleration.

Front 13

Centripetal Acceleration Equation

Back 13

ac=v^2/r

Front 14

By subbing centripetal equation into Fnet=man this equation is found

Back 14

Fc=mv^2/r

Note: Fc is the net force in this motion.

Front 15

The outward feeling

Back 15

Related to momentum. Explained by considering newton's laws.

For instance, car turning with a ball in it's tray. 1st law. As the car turns the ball continues in a straight line, appears to move outwards. Later, the ball reaches the side of the tray which exerts a horizontal force on the ball causing it to follow the car and move in circular motion.

Front 16

Torque

Back 16

A turning force. Vector. Clockwise or anticlockwise. Units Newton metres N m.

Front 17

Torques size depends on?

Back 17

The size of the applied force and the distance that the force is applied from the pivot point (fulcrum).

Front 18

Torque equation

Back 18

T=Fd

D=perpendicular distance

Front 19

Equilibrium

Back 19

When an object or system is at equilibrium all it's forces and torques are balanced and the object or system will not accelerate or rotate.

Front 20

1st condition of equilibrium

Back 20

ET=0 the sum of the clockwise torques equals sum of anticlockwise torques

Front 21

2nd condition of equilibrium

Back 21

EF=0 the sum of all the translational forces adds to zero. Upwards forces sum = sum of all downwards and the sum of left-acting forces equal right-acting forces sum.

Front 22

Where are anticlockwise and clockwise torques?

Back 22

To right of fulcrum clockwise

To left of fulcrum anticlockwise

Front 23

When subbing into torque equation

Back 23

The distance away from the fulcrum is D, ie for a seesaw example.

Front 24

Double pivot questions

Back 24

1) if asked to find size of upwards force provided by one of the supports (A), then make the other support (B) the fulcrum.

2)if asked to find size of upwards force provided by both supports, it doesn't matter which support is used as the fulcrum.

Front 25

Clockwise or anticlockwise for fulcrum in double pivot questions?

Back 25

In direction of force

Front 26

Balanced torque can be used to find?

Back 26

Tension force in angled supports.

Front 27

For. Torque to exist?

Back 27

Distance and force must be perpendicular

Front 28

Answering torque questions

Back 28

Where the horizontal meets the vertical = pivot point

The tension force along the hypotenuse is found using trigonometry, though first you must find the vertical force component by considering torques on the object.

Clockwise torques are the horizontal.

Anticlockwise torques are the diagonal.