Forces Flashcards
6 scalar quantities
mass
temp
speed
energy
distance
time
what makes a quantity scalar
have magnitude only
no direction
6 vector quantities
velocity
displacement
weight
acceleration
momentum
force
what makes a quantity vector
has magnitude +direction
what are vectors reperesented with
an arrow
length of arrow represents…
magnitude of vector
define force
a push or pull that acts on an object due to the interaction
with another object
are forces scalar or vector
vector
unit for force
newton
2 catogories for forces
contact
non contact
what is meant by contact force
objects physically touching
what is meant by non contact force
objects physically separated
what is meant by non contact force
objects physically separated
4 eg contact force
tension in rope
friction
air resistance
normal contact force
what does force of tension do in tug of war
force of tension pulls on the person
what does force of friction do when aeroplane lands on sea
force of friction causes plane to slow down and stop
what happens when sky diver falls through air
air particles collide with parachute
force of air resistance acts upwards
when does a normal contact force happen
when objects are in direct contact
normal contact force:
what type of force does lamp exert on table
lamp exerts downward force on table which is its weight
normal contact force:
what does table do
exert upwards force on lamp
3 eg non contact force
gravitational force
electrostatic
magnetic force
what does gravitational force do
attracts all objects to other objects
the electrostatic force is the force between
2 charged objects
what is experienced by objects with opposite forces
electrostatic force of attraction
what is experienced by objects with the same type of charge
electrostatic force of repulsion
what is the magnetic force
force experienced by certain objects in a magnetic field
gravity is a force of……
attraction between all objects
is gravity vector or scalar
vector
what does mass of an elephant tell you
how much matter in the elephant
unit of mass
kj
is mass scalar or vector
scalar( no direction)
does mass change depending on where object is ?
no
does mass change depending on where object is ?
no
the weight of an elephant is the
force acting on the elephant due to gravity
unit for weight
newton
does weight change depending on where object is ?
yas
symbol for gravitational field strength
g
gravitational field strength is a measure of
the force of gravity in a particular location
what amount of force do objects on surface of earth experience
force of 9.8N for every kg of their mass
unit for gravitational field strength
N/Kg
weight and mass of object are directly or indirectly proportional?
directly
what does directly proportional mean
if we double mass, weight also doubles
how to work out objects weight
use calibrated spring balance ( newtonmeter)
does gravitational field strength depend on location
yes
define meaning of objects centre of mass
The weight of an object may be considered to act at a single point
define force
push/ pull that acts on object
due to interaction with another object
are forces vector/ scalar
vector
what is resultant force
single force that has same effect as all the original forces acting together
how to work out resultant force
larger force minus smaller force
give example when resultant force is 0
skydivers weight is 800N (downward force)
air resistance is 800N (upward force)
how are free body diagrams drawn
object shown as a point
forces drawn as arrows starting at the point
what does length of arrow in free body diagram show
strength of force
what does altitude mean
height above ground
describe free body diagram for plan flying at constant altitude and constant velocity
dot in centre of 4 arrows
arrows at right angles to each other
lift acts upward
weight acts downward
air resistance to left
thrust to right
lift and weight arrows same length
air resistance and thrust arrows same length
^
l <--- 0 --->
l
How would you solve this question?
Two forces are acting on an object. One force has magnitude of 10 N. Another force has magnitude of 8N. Angle between the two forces is 30 *. Calculate resultant force
Make vector/ free body diagram for the two forces involved
say 1cm = 1N
put point on page.
use ruler, draw 10cm long arrow (for the 10N force)
use protractor to measure angle of 30*
Use ruler to draw 8cm long arrow ( for 8N force)
Now make a paralellogram
copy the 8cm line, at the head of the 10cm arrow
copy the 10cm line , at the head of the 8cm arrow
make sure exterior angles are 30*
Draw lines from tail of vectors to opposite side
(horizontal line splitting parallelogram in two)
