Physics Exam Revision

Newton’s First Law

Newton’s First Law

Every object remains at rest, or continues with constant velocity, unless it experiences an unbalanced force. Aka law of intertia

Newton’s Second law

The acceleration of a body experiencing an unbalanced force is directly proportional to the net force acting on it and inversely proportional to the mass of the body.

Newton’s third law

When one body exerts a force on another body (an action force), the second body exerts an equal force on the first body but in the opposite direction (a reaction force)

Action-Reaction Pairs

• Are the same magnitude

• Act in opposite directions

• Act on two different objects

Constant Acceleration Equations

0

when forces are balanced, the net force = ?

Law of Inertia

tendency to resist motion or change in motion

often not observed

Newton’s First Law is ______ in real life

ma (mass * acceleration)

F_net =?

F_net/m (Net force over mass)

a (acceleration) = ?

use the area under the graph

conversion of acceleration to velocity using graph

use the area under the graph

conversion of velocity to displacement using graph

use the gradient of the graph

conversion of velocity to acceleration using graph

use the gradient of the graph

conversion of displacement to velocity using graph

Centripetal acceleration

An object accelerating towards the centre of its path. Given as a = v²/r and v = 2πr/T

Force required for circular motion

F = ma = (mv²)/r (Newton’s second law)

towards the centre

centripetal motion acts?

uniform circular motion

• constant speed

• constant radius

• velocity is tangential to the path of travel

• change in direction of velocity is radial towards the centre

• net force towards the centre

tangential

90 degrees from a certain path

acceleration

change in direction of velocity

period

time taken to complete one revolution

frequency

rotations per second

speed in circular motion

d/t = circumference over period = 2πr/T

frequency formula

F = 1/T

properties of circular motion with flat tracks

The vehicle relies entirely on friction between the tyres and road to provide the centripetal force for circular motion

flat track

a completely smooth track that allows objects to have a normal force parallel to the gravitational force

friction is insufficient

If the ___________, the vehicle cannot follow the circular flat path, departing at a tangent

properties of circular motion with banked tracks

The net force toward the centre includes both friction and a component of the normal force

banked tracks

tracks at an angle to the ground, meaning objects do not have a normal force parallel to the gravitational force

normal force

the force exerted by a surface to support the weight of an object resting on it, acting perpendicular to the surface

normal force on banked tracks

will be greater than that on a flat track

Design speed

The speed at which no sideways frictional force is required, and depends on the angle

centre

An object in horizontal circular motion has an acceleration towards the _____ of the circle

magnitude and direction

in horizontal circular motion, the _______ change

constant speed

Vertical circular paths do not usually involve _______

Uniform horizontal motion

• No unbalanced forces

• Normal force balances the gravitaional force

forces on an object at rest

F_N and F_g = 1G

Circular motion through dips

• Net centripetal acceleration is upwards due to circular path

• Normal force and force due to gravity are unbalanced

• Normal force greater than the ‘usual’ balance of force due to gravity

• seat feels heavier than normal/pushing up more

Circular motion over humps

• Net centripetal acceleration downwards due to circular path

• Normal force and force due to gravity not in balance

• Normal force less than the ‘usual’ balance of force due to gravity

• You feel the seat pushing up less/lighter than normal

Circular motion through loops

• You don’t fall if the centripetal force is greater than the force due to gravity

• When the cart is at the critical speed where the cart just stays in contact / is about to fall, the normal force is zero

• The force due to gravity does not change

• The normal force varies throughout the motion

gravity

the only force acting on a projectile that is launched at an angle to the horizontal is?

downwards

when gravity is the only force on an object, the force arrow will always point?

constant

horizontal velocity will remain _____ when there are no restraining forces

horizontal velocity

gravity has no effect on __________

9.8 m/s/s

the value for gravitational acceleration is?

highest point

the vertical velocity will be zero at the?

at its lowest

at the highest point of its trajectory, the kinetic energy of a launched object will be?

trigonometry

What do you use to resolve horizontal and vertical components?

constant acceleration equations

What do you use to resolve for time, distance, velocity?

time and constant acceleration equations

What do you use to solve for horizontal distance?

collisions

when there is motion, there may be?

momentum

the product of an objects mass and its velocity

vector

momentum is a ______ quantity

law of conservation of momentum

in any collision between objects in an isolated system, the total momentum of the system is conserved

sum of initial momentum

the sum of final momentum is equal to the:

-1 * Force on B by A

Force on A by B = ?

impulse

the change in momentum of an object

calculating impulse with graphs

area under Force vs time graph

force formula through momentum

impulse using force vs time

impulse using mass and velocity

impulse formula

work has been done

when a force acts on an object, causing a change in its displacement, we say?

work

the transfer of energy from on object to another, or the transfer of energy from one form to another

W = Fs

work formula when force is constant

W = Fs cos theta

work formula when force is applied at an angle to displacement

the change in energy

work can be expressed as?

vector

force is a _____ quantity

vector

displacement is a ____ quantity

scalar

work is a _____ quantity

scalar

energy is a _____ quantity

net force

use the _______ when calculating the work done on an object

no

is work being done when an object is being held stationary?

no

is work being done when an object is in circular motion?

no work has been done

when there is no displacement in the direction of the force, _________________________ on the object by that force

the area under the force vs displacemnt

work done when force is not constant

elastic potential energy

energy stored in material when it is stretched or compressed

potential energy

energy of an object due to its displacement

elastic

If the material is ______, then the energy can be returned to the system when the material returns to its original shape

If the material is ______, then the material will undergo permanent changes

hooke’s law

describes how the size of a force exerted by a spring is proportional to the length of extension or compression, and the force is in the opposite direction to the extension or compression

kinetic energy

the energy of motion of an object

½ mv²

kinetic energy for low-speeds (non-relativistic)

perfectly elastic collision

kinetic energy is transferred between objects with no energy loss or wastage

kinetic energy before = kinetic energy after

elastic collisions in a closed system

inelastic collisions

kinetic energy is ‘lost’ or wasted through transformation

false

most day-to-day collisions are perfectly elastic

almost elastic collisions

collisions with very little energy transformed

examples of almost elastic collisions

newton’s cradle and snooker ball collisions

collisions between subatomic particles

example of perfectly elastic collisions

gravitational potential energy

the energy stored in an object due to its position in a gravitational field

formula for gravitational potential energy

area under force vs distance graph

how to find changes to gravitational potential energy?

mechanical energy

energy associated with the motion and the position of an object

examples of mechanical energy

• heat

• sound

• kinetic energy

• potential energy

energy transformations

the change of energy from one form to another

law of conservation of energy

While energy can be transformed to different forms of energy, or transferred between objects, it cannot be created or destroyed

mechanical energy formula

sum of kinetic and potential energy of an object

closed system

mechanical energy is constant in a ________