physics p2 : forces

whats a scalar

a quantity that only has magnitude (size) e.g 22 m/s

what are some examples of scalar quantities

speed, distance , mass , temperature and time

whats a vector

a quantity with magnitude __and__ direction e.g 22 m/s north

what are some examples of vector quantities

velocity, displacement, acceleration and momentum

whats speed definition

how fast an object covers distance

what is the symbol and unit for time

symbol : t

unit : s

is speed a scalar or a vector quantity

scalar

whats the equation for speed

distance travelled (m) = speed (m/s) × time (s)

what is acceleration definition

the rate of change in velocity

is acceleration a scalar or a vector

vector

what is the equation for acceleration

acceleration (m/s ) = change in velocity (m/s) / time (s)

whats the equation for acceleration when given distance

(final velocity )^2 - (initial velocity)^2 = 2 x (acceleration) (distance)

what does it show when the acceleration is negative

its slowing down (deceleration)

whats the symbol and unit for acceleration

symbol : a

unit : m/s ^2

whats displacement

how far you are from the start and in what direction

what is the formula for displacement

Displacement = Final position – initial position = change in position.

is displacement a scalar or a vector quantity

vector

whats the symbol and unit for displacement

symbol : s

unit : m

whats the velocity

the speed of something in a given direction

is velocity a scalar or a vector quantity

vector

whats the equation for velocity

velocity = displacement / time

whats the symbol and unit for final velocity (finish speed)

symbol : v

unit : m/s

whats the symbol and unit for initial velocity

symbol : u

unit : m/s

whats the magnitude

the size

whats the equation for momentum

momentum = mass x velocity

is momentum a scalar or a vector quantity

vector

how do you calculate the momentum for a number of objects

adding them all together

what does the gradient of a distance time graph represent

how fast an object is moving ( the velocity)

what does the a steady line show on a distance time graph

steady speed

what does a flat line show on a distance time graph

no movement

what does a steep line on a distance time graph show

faster

what is there no such thing as on a distance time graph

a negative line

what does a line coming down show on a displacement time graph

returning to start

what does this distance time graph show us

its accelerating

how do you calculate the gradient(speed) on a distance time graph

speed = distance/ time

how do you calculate the gradient on a velocity time graph

change in velocity/ time (same as acceleration)

how do you find the distance travelled in a velocity time graph

find the area

whats a force

a push or pull that acts on an object due to the interaction with another object

what are contact forces

forces that act between two objects that are physically touching each other

what are non contact forces

forces between two objects that aren’t touching

whats an example of a contact force

friction

what are examples of non contact forces

electrostatic, magnetic and gravitational forces

whats an interaction pair

a pair of equal and opposite forces acting on two different objects

whats a resultant force

the overall force on a point or object

is a force a vector or a scalar

vector

what is a free body force diagram

a diagram of an object with arrows drawn to show the direction and size of the forces acting on the object

whats a non zero resultant force

it means the forces are unbalanced

how do you use scale drawings to find the resultant force

• draw a scale diagram drawing the forces tip to tail and using a sensible scale (e.g. 1cm=1N)

• measure the length if the resultant force by measuring from the start of the first force to the end of the last force

when is an object in equilibrium

if all the forces on an object are balanced

the forces acting on an object are drawn to scale and tip to tale, forming a closed loop. What does this say about the resultant force acting on an object

the resultant force is 0 as the forces are balanced

what does it mean when you resolve a force?

you split the force into 2 forces that are at right angles to each other. The two forces have the same original effect as the original force

whats newtons first law

an object will remain stationary or at a constant velocity unless acted upon by an external force

whats newtons second law

the force acting on an object is equal to its rate of change of momentum (meaning any resultant force will produce an acceleration)

whats the formula for newtons second law

force = mass x acceleration (F=ma)

what happens if there is no resultant force on a moving object

it will carry on moving at the same velocity

what do you need to keep moving when there is friction

a driving force (e.g. thrust)

what does an object do if the driving force is equal to the friction force

the object will stay at a steady speed

what does an object do if the driving force is greater than the friction force

the object will accelerate

what does an object do if the driving force is less than the friction force

the object will decelerate

what is terminal velocity

• as the air resistance increases, so will the air resistance

• terminal velocity is when the air resistance equals the weight and the resultant force equals 0

whats the resultant force

the combination of all the forces acting on an object

what causes air resistance

the moving object colliding with the particles of air

The size of the air resistance is dependent on the object's ______.

surface area and it velocity

We say an object has reached 'terminal velocity' when it is falling with a _________ velocity.

constant

what is inertia

how difficult it is to change an objects velocity

whats the forumla for interial mass

force / acceleration

whats newtons 3rd law

when two objects interact, the forces they exert on each other are equal and opposite

whats the normal contact force

the force that surfaces exert to prevent solid objects from passing through each other

how do objects move forward if according to newtons 3rd law the forces objects exert on each other are equal and opposite

a high force or a small mass

whats the equation for momentum

momentum = mass x velocity

whats the unit used for momentum

• kgm / s

• kiloram metres per second

whats the law of conservation of momentum

in a collision when no other external forces act, momentum is conserved (the total moment after the collision if the same as it was before it)

whats the equation linking change in momentum, force and time

force x time = change in momentum

whats an elastic collision

where the total energy in the kinetic energy stores colliding is the same before and after the collision

whats a inelastic collision

where some of the energy in the kinetic energy stores is transferred to others stores

what is gravity

the force of attraction between masses

what is meant by the weight of an object

the force acting on an object due to gravity

what is the equation for gravitational force (weight)

weight = mass x gravitational field strength

w = mg

what is gravitational potential energy

the energy it has due to its height in a gravitational field

what is the equations for gravitational potential energy

gravitational potential energy = mass × gravitational field strength × height

gpe = mgh

what 2 factors affect the strength of gravitational attraction between 2 objects

• the mass

• the distance

whats kinetic energy

the kinetic energy of an object is the energy it possesses due to motion

whats the formula for kinetic energy

kinetic energy = 1/2 × mass × (speed)2

what is power

the rate at which energy is transferred, or the rate at which work is done

whats the formula for power

power = energy / time

p = E/t

what is work done

refer to the energy transfer that occurs when a force is used to move an object by a certain distance

whats the unites for work done

watts

whats the equation for work done

work done = force × distance

W = F s

whats inelastic deformation

the change in the shape of an object which can not be reversed once the forces that are stretching it have been removed (object will not return to original shape)

what does spring contant mean

a measure of how many newtons or force