p5 Flashcards
what is a quantity?
a property that can be given a number and therefore can be measured or calculated
what is a scalar quantity?
quantities with only magnitude i.e size
what is a vector quantity?
quantities with both magnitude and direction
name five scalar quantities
- energy
- time
- distance
- speed
- temperature
name six vector quantities
- forces
- momentum
- displacement
- velocity
- acceleration
- current
go down five from base unit
- milli
- micro
- nano
- pico
- femto
what is distance?
- scalar quantity:
the length of the path between start and finish
what is displacement?
- vector quantity
how far you’ve travelled from the start in a straight line and includes direction
what is velocity ?
velocity is speed in a given direction
what is the equation for speed?
speed = distance/ time
what is the equation for velocity?
velocity = displacement/ time
what is a force?
a force is a push or pull
what three things can a force change about an object ?
- speed
- direction
- shape
what are the three non contact forces?
- weight
- magnetic
- electrostatic
what are contact forces?
contact forces are forces that can act between objects when they are touching
what are non contact forces?
non contact forces are forces that can act between objects which are not touching
name the six contact forces
- normal contact force
- upthrust
- driving force / thrust
- air resistance / drag
- friction
- tension
what is electrostatic force?
force of attraction/ repulsion between charged objects
what is magnetic force?
force of attraction/ repulsion between magnetic poles or magnetic matetials
what is resultant force?
the overall force acting on an object.
it has both magnitude and direction
what is mass?
the mass of an object is a measure of how much matter it is made of
it is the same everywhere in the universe
what are the units for mass?
kilograms (kg)
how is mass measured?
using a top pan balance
explain the concept of gravity
- all objects with a mass have gravity which attracts other objects with a mass towards it
- the greater the mass the stronger it’s gravity
- hence, why only the gravity of massive objects like stars and planets are noticeable
- strength of an objects gravity is defined by the gravitational field strength
what is weight?
weight is the force acting on an object, due to another objects gravity
what are the units of weight?
Newtons (N)
what two factors does weight depend on?
- the mass of the object
- the gravitational field strength at that particular location
how is mass measured?
Newton meter
what is the equation for weight?
W = m x g
weight = mass x gravitational field strength
W: Newtons (N)
m: kilograms (kg)
g: Newtons per kilogram (N/kg)
what is the centre of mass?
the centre of mass of an object is a point at which the weight is considered to act
equation for work done
W = F x s
work done = force x distance
what are the four ways of describing motion in an object?
- stationary
- constant speed/ velocity
- accelerating
- decelerating
what is constant speed/ velocity?
distance travelled each second is constant
what is acceleration?
rate of change in velocity
(speed is increasing by the same amount every second)
equation for speed
speed = distance/ time
equation for velocity
velocity = displacement / time
two equations for acceleration
acceleration = change in velocity/ time taken
acceleration = final velocity - initial velocity / time taken
units: acceleration = m/s^2
equation to work out constant acceleration
v^2 - u^2 = 2as
v: final velocity (m/s)
u: initial velocity (m/s)
a: acceleration (m/s^2)
s: distance or displacement (m)
explain why an object moving in a circle at a constant speed is accelerating (3)
- acceleration is the rate of change in velocity
- velocity is a vector quantity so
- when moving in a circle, whilst magnitude is constant, direction changes causing velocity to change
what is free - falling?
- object only has weight acting on it
- there are no resistive forces such as air resistance or friction
- near earths surface, free falling objects have a downwards constant acceleration of 9.8m/s^2
how can the speed of a car be determined using a single light gate?
- measure the length of the car to use as the distance with a ruler
- use a timer to measure the time in which the light gate was blocked
- use the equation speed = distance/ time to calculate speed
what does the gradient of a velocity-time graph show?
acceleration or deceleration
what does the area under the line of a velocity-time graph show?
displacement
what does the gradient of a distance-time graph show?
speed
how do you determine instantaneous motion of a motion-time graph?
calculate gradient of tangent
equation for resultant force
F = m x a
F: Newtons (N)
m: kilograms (kg)
a: metres per second squared (m/s^2)
what is newton’s first law ?
objects will remain at rest, or continue moving with a constant velocity unless acted on by an additional force
what is newton’s second law?
acceleration is directly proportional to the resultant force acting on an object when mass is constant
acceleration is inversely proportional to the objects mass when resultant force is constant
what is newton’s third law?
when two bodies interact with each other, they exert equal and opposite forces of the same type on eachother
what is inertia?
the tendency id an object to continue in its current state (at rest or constant velocity)
with reference to newtons laws, explain why a gun recoils when a bullet is fired (3)
when the bullet is fired
there was a forward force exerted on the bullet by the gun
according to newton’s third law, the bullet exerts an equal and opposite (backwards) force ok the gun, hence why it recoils
what is stopping distance?
the sun of the thinking distance and the braking distance
what is the thinking distance?
distance travelled during the drivers reaction time
what is braking distance?
distance travelled under braking force
what factors increase thinking distance?
- tiredness
- taking drugs
- drinking alcohol
- using a phone
what factors increase braking distance?
reduce friction between road and tyres by:
- wet/ icy roads (poor weather conditions)
- potholes (poor road conditions)
- worn out tyres (poor vehicle conditions)
reduce braking force applied:
- worn out/faulty breaks
what is the relationship between thinking distance and speed?
directly proportional
state the equation that links extension, force and spring constant
F = ke
force = spring constant x extension
state the equation that links distance, force and moment of a force
M = Fd
moment of a force = force x distance (perpendicular to the direction of the force)
state the equation that links area, force and pressure
P = F/A
pressure = force normal to a surface/ area of surface
state the equation that links acceleration, mass and resultant force
F = ma
resultant force = mass x acceleration
state the equation that links mass, momentum and velocity
p = mv
momentum = mass x velocity
state the equation that links density, gravitational field strength, height, and pressure
p = h p g
pressure = height of column x density of liquid x gravitational field strength
state the equation that links acceleration, distance, initial velocity and final velocity
v^2 - u^2 = 2as
state the equation that links force, momentum and time
F = mass x change in velocity/ time
how do you prove inverse proportion on a graph?
for at least 3 data points, x*y = constant
what is a closed system?
there is no external force actint on it
what is the law of conservation of momentum?
in a closed system, the total momentum before a collision or separation is equal to the total momentum after
what is the sentence structure for how to reduce impact forces?
- how does the safety device work?
- safety device increases the impact time
- this decreases the rate of change of momentum
- this reduces the impact force and decreases the chance of serious injury
what is pressure?
pressure is the force exerted per unit of area
explain how tractors having tracks rather than conventional wheels prevents them from sinking into the mud (3)
TIP: determine what equation and value is constant to find the rule to apply
- of the weight of the tractor (force exerted) is constant
- pressure is inversely proportional to the area
- the tracks provide a greater surface area
- thetefore, for the same forge applied, the pressure exerted by the tracks will be less
what is fluid pressure?
the force exerted per unit area due to collisions between the particles of the fluid and the container wall
why does fluid pressure increase with depth?
- at a given depth there is a column of fluid above it
- as depth increases, the height of the column increases
- therefore the weight of the column and the force it exerts per unit of area at that depth increases
describe and explain how atmospheric pressure changes with increasing altitude (4)
- as altitude increases, atmospheric pressure decreases
- this is because as altitude increases, the height of the column of air above decreases and the density of are also decreases
- therefore, the weight of the column decreases because the mass of the air particles above decreases
- hence the force exerted per unit area decreases
at the top of the mountain, the lid is closed on an empty bottle. as the hiker makes his way down the mountain the bottle changes shape. explain why. (3)
- at the top of the mountain when the bottle is closed the pressure of the air inside the bottle is equivalent to the atmospheric pressure.
- when the bottle is brought down the mountain, atmospheric pressure increases whilst gas pressure inside the bottle remains constant so it is greater than gas pressure inside the bottle
- so the bottle is crushed
what three things can happen when more than one force is applied to a stationary object?
- extent
- compress
- bend
what is elastic deformation?
elastic deformation occurs when the object recurs to its original shape after the applied force is removed
what is plastic/ in elastic deformation?
occurs when the object does not return to its original shape when the applied force is removed
hookes law states that…
the extension of an elastic object is directly proportional to the force applied up to the limit of proportionality
what is the limit of proportionality?
the point beyond which the extension is no longer directly proportional to the force
what does the spring constant of a spring indicate?
the stiffness
the greater the spring constant, the stiffer the spring
what is a moment?
the moment is the turning effect of a force about a pivot
what are two ways to increases the moment?
- increase the magnitude of the force applied
- increase the perpendicular distance between the force and the pivot
what is the principle of moments?
when an object is balanced about a pivot (in equilibrium) the total clockwise moment is equal to the total anti-clockwise moment
