Forces Flashcards
what is a scalar quantity?
something that only has magnitude (size)
three examples of scalar quantities
- mass
- temperature
- speed
what is a vector quantity?
something that has both direction and magnitude
three examples of vector quantities
- velocity
- weight
- force !!
define what a force is
a push, pull, or twist that acts on an object due to interaction with other objects
what is force measured in?
newtons (N)
three examples of a contact force
- friction
- air resistance
- reaction
three examples of non-contact forces
- gravity
- magnetism
- electrostatic
define what weight is
a force due to gravity
what is weight measured in?
newtons (N)
what is the equation for weight?
weight = mass x gravitational field strength
what is the connection between weight and mass?
they are directly proportional to one another
define resultant force
a single force that is used to represent a number of forces acting on an object
what is the connection between work done and energy transfer?
whenever work is done, energy is transferred
key fact about elastic materials
they will always return to their original shape if we take away the forces acting on them
define elastic limit
the point at which a spring does not go back to it’s original shape
what’s the connection between work done and elastic potential energy?
the work done is equal to the elastic potential energy
describe the differences between distance and displacement (2)
DISTANCE
- only shows how far
- scalar quantity (only has magnitude)
DISPLACEMENT
- shows how far an object travels in a given direction
- vector quantity (has both magnitude and direction)
what is the typical walking speed?
1.5 m/s
what is the typical running speed?
3 m/s
what is the typical cycling speed?
6 m/s
what is the speed of sound in air?
330 m/s
how can you work out the speed of sound? (5)
- stand near a wall in a place that echoes (hall, sports hall)
- two people: one holds the stopwatch, one claps their hands
- measure your distance from the wall
- time how long from clapping that the echo is heard for
- use the speed equation
define velocity
speed in a given direction
what is the one difference between calculating speed and calculating velocity?
when calculating velocity, the answer must state the direction in which the object is moving in
*e.g - 1.25 m/s south*
how do you work out the gradient from a distance-time graph?
gradient = distance travelled
————-
time taken
define acceleration
how fast there is a change in an object’s velocity
what exactly does the gradient of a velocity-time graph tell us?
the acceleration
define deceleration
negative acceleration
how do you work out displacement from a velocity-time graph?
calculate the total area under the graph
define terminal velocity
when the forces acting against an object balance and the object therefore stops accelerating and moves at a constant velocity
Newton’s First Law (3)
> if a force acts on a stationary object, it will cause it to move
if a force acts on a moving object, the object will either:
- slow down
- speed up
- change direction
> if the overall force is balanced then…
- a stationary object will remain stationary
- a moving object will continue to move at a constant speed
Newton’s Second Law (3)
> force is directly proportional to mass
- the greater the mass, the larger the force it will exert
> force is directly proportional to acceleration
- the greater the force, the greater the acceleration
> acceleration is inversely proportional to mass
- the greater the mass, the less acceleration to mass
Newton’s Third Law
> whenever two objects interact, the forces they exert on each other are equal and opposite
define stopping distance
the overall time taken to stop after seeing an obstruction
what makes up stopping distance?
thinking distance + breaking distance
define thinking distance
time taken to apply the break once seeing an obstruction
define breaking distance
how long it takes the car to stop after the break has been applied
list the factors that affect thinking distance (6)
- speed
- age
- distractions
- tiredness
- alcohol
- drugs
list the factors that affect breaking distance (3)
- speed
- brake conditions
- weather
list the dangers of rapid deceleration (2)
- driver could lose control of the car
- brakes overheat
conservation of momentum
total momentum after the event is equal to the total momentum before the event
