Mechanics

Question 1

Scalar quantity

Answer 1

Has no direction, only magnitude
For example, mass, speed, distance etc.

Question 2

Vector quantity

Answer 2

Has a magnitude and direction
For example, velocity displacement force, et cetera

Question 3

Forces in equilibrium

Answer 3

If an object is an equilibrium, all the forces acting on it are balanced and cancel each other out
An object in equilibrium can be at rest or moving with constant velocity

Question 4

Inertia

Answer 4

A measure of how much an object resist a change in velocity
The larger the inertia of an object the larger applied force needed to change its velocity by given amount

Question 5

Moments

Answer 5

A moment is the turning effects of a force around turning point
The moment of a force depends on the size of the force and how far the forces applied from the turning point

Question 6

Principle of moments

Answer 6

The principle of Mum states that for a body to be an equilibrium the sum of the clockwise moments about any point equals the sum of the anticlockwise moments about the same point
If the objects are unbalanced, the object will turn

Question 7

Moments in levers

Answer 7

In a lever and effort force acts against the load force by means of a rigid object rotating around a pivot
They increase distance from the pivot are force as applied so you need less force to get the same moment

Question 8

Couples

Answer 8

A couple is a pair of forces of equal size which acts parallel to each other but opposite directions
A couple doesn’t cause any resultant linear force that does produce a turning effect
Size of the moment depends on the size of the forces and the distance between them

Question 9

Centre of mass

Answer 9

The centre of mass of an object is the single points that you consider the whole weight to act through
The object will always balance around this point

Question 10

Newton’s first law

Answer 10

The velocity of an object will not change unless a resultant force acts on it

Question 11

Newton second law

Answer 11

The acceleration of an object is proportional to the resultant force acting on it
F = m x a

Question 12

Newton’s third law

Answer 12

If an object A exerts a force on object B, then object B exerts an equal but opposite force and object A

Question 13

Projectile motion equation

Answer 13

s = 0.5 gtt

Question 14

Drag

Answer 14

Air resistance causes a drag force that acts in the opposite direction to motion and affects the trajectory of a projectile

Question 15

Friction

Answer 15

A force that oppsoses motion

Question 16

Two main types of friction

Answer 16

Contact and fluid friction

Question 17

Contact friction

Answer 17

Happens between solid surfaces

Question 18

Fluid friction

Answer 18

Fluid friction is known as drag, or fluid resistance or air resistance

Question 19

Three things that affect fluid friction

Answer 19

-The force depends on the thickness or viscosity of the fluid
-the force increases as speed increases
- force depends on the shape of the object moving through it - the larger the area pushing against the fluid, the greater the resistance force

Question 20

Three things to remember about frictional forces

Answer 20

-they act in opposite direction to the motion of the object
-They can never speed things up or start something moving
- they covert kinetic energy into heat

Question 21

Lift

Answer 21

The upwards force on an object moving through a fluid. It happens when the shape of an object causes the fluid flowing over it to change direction
The force acts perpendicular to the direction in which the fluid is flowing

Question 22

Terminal speed

Answer 22

Happens when frictional forces equal the driving force
An object will reach a terminal speed at some point if there’s a driving force that stays the same all the time and a frictional or drag force that increases with speed

Question 23

Momentum

Answer 23

Linear momentum depends on its mass and velocity
Momentum = mass x velocity

Question 24

The principle of linear momentum

Answer 24

Assuming no external forces act, linear momentum is always conserved
Meaning total linear momentum of two objects before they collide equals the total linear momentum after the collision

Question 25

Elastic collisions

Answer 25

Where momentum is conserved and kinetic energy is conserved
No energy is dissipated as heat, sound, et cetera
Ek = 0.5 m vv

Question 26

Inelastic collisions

Answer 26

Means some of the kinetic energy is conserved in other forms during the collisions
Linear momentum is always conserved in inelastic collisions

Question 27

Impulse

Answer 27

Impulse is defined as the product of force and time
So the impulse on a body is equal to the change in momentum of that body and is measured in newtons

F△t = △(mv)
F △t = impulse in Ns
△(mv) = change in momentum

Question 28

Impulse equation

Answer 28

F△t = △(mv)
F △t = impulse in Ns
△(mv) = change in momentum

Question 29

Calculating Work done

Answer 29

W = Fs
W = Work done
F = force causing motion in newtons
s = Distance moved in metres

Question 30

Power and Work

Answer 30

P = △W/△t
P = power in watts
△W = work done in joules
△t = time in seconds

Question 31

Forces at an angle

Answer 31

W = Fs cos(theta)
Theta = angle at which the force acts from the direction of motion

Question 32

Equation for moving objects for power

Answer 32

P = Fv
P = power in watts
F = for causing the motion in newtons
v = speed in the direction of motion ms^-1

If working at angle :
P=Fv cos(theta)

Question 33

The principle of conservation of energy

Answer 33

Energy cannot be created or destroyed
Energy can be transferred from one form to another, but the total amount of energy in a closed system will not change

Question 34

Equation for elastic potential energy

Answer 34

E = 0.5k (△L)^2
E = elastic potential energy in joules
k = stiffness in an object in Nm
△L = extension of the material

Question 35

Transfers between kinetic and potential energy

Answer 35

0.5mvv = mg △h