SUMMARY SHEET FOR GRADE 10 SUMMER PHYSICS EXAMS
PRESSURE IN FLUIDS equation (gravity X height X density) 10hd
pg103
PASCAL’S PRINCIPLE: the pressure exerted on the surface of an enclosed fluid is equally transmitted throughout the
fluid. car brakes (Physpap3 1999#3) hydraulic systems (enclosed fluids)
ARCHIMEDES PRINCIPLE: Any object totally or partially immersed in a fluid experiences an upthrust force which is equal
to the weight of the displaced fluid. pg106
Upthrust force = weight of displaced fluid
Weight = mass in kg X gravity
upthrust force = weight in air – weight when immersed in fluid
WEIGHT of displaced fluid = weight of beaker with fluid in it – weight of empty beaker.
HOOKE’S LAW: The extension of a spring is directly proportional to the applied force as long as the elastic limit of the
spring is not reached.
WORK: Force X distance moved in the direction of the force (Nm or J) pg 98
POWER: The rate of doing work or converting energy. Power= work/time power= energy/ time (J/s or Watts (W))
KINETIC ENERGY (J): the energy a body has by reason of its motion ( ½ MASS x VELOCITY SQUARED)
½ mxV2
POTENTIAL ENERGY (J): Gravitational potential energy (mass X gravity X height above ground) mgh
MACHINES: a device where one force applied (effort) at one point, over comes another force (load) acting at another
point. Simple machines: levers, FLE classification and examples.
MECHANICAL ADVANTAGE M.A. = load/ effort
VELOCITY RATIO V.R. = distance moved by effort / distance moved by load in the same time
EFFICIENCY= (work output / work input) X100%
efficiency = (M.A./V.R) X 100%
PULLEYS: single fixed M.A. = 1 single moving M.A. = 2 block & tackle M.A. = total number of string with tension in
them or total number of pulleys in system (use arrows for each force)
INCLINED PLANES: M.A. = (length of plane / height of plane)
V.R. = (length of plane / height of plane)
distance moved by effort = length of plane
distance moved by load = height of plane
SCREWS: work input = work output
effort x distance moved by effort = load X distance moved by load
distance moved by effort = 2 x pi x r where r is the length of the tommy bar
distance moved by load = the pitch of the screw
MOMENT OF FORCES: (turning effect) moment of force = force X dist away from pivot (Nm)
PRINCIPLE OF MOMENTS: for a uniform object in equilibrium, the sum of the anticlockwise moments is equal to the sum
of the clockwise moments. Use principle of moments to find force, distance from fulcrum, and weight of uniform
object. (Always draw the diagram)
LINEAR MOTION: scalar quantities: have only magnitude e.g. distance, speed. Vector quantities: have both magnitude &
direction e.g. displacement, velocity, acceleration, all forces
average speed = total dist / total time (m/s)
displacement is distance in a certain direction (m)
speed is rate of change of distance (m/s)
velocity is the rate of change of distance in a particular direction or rate of change of displacement (m/s)
acceleration is rate of change of velocity (m/s2)
acceleration = (final velocity – initial velocity)/ time or (V-U)/t
MOTION GRAPHS:
DISTANCE- TIME GRAPHS or displacement – time graphs
read off distance and time from the axes, straight line through the origin means constant speed or velocity. To find that
speed read off dist from the axis and divide by time on the x axis.
Straight line parallel to the x axis means no motion (at rest)
SPEED-TIME GRAPH or velocity- time graph
Read off speed(or velocity) and time from the axes
Straight line through the origin means constant acceleration. To find that acceleration use (V-U)/t Straight line parallel to
the x axis means constant speed (or velocity) read that off the y axis
straight line going back to the x axis means constant deceleration. To find the deceleration use (V-U)/t (answer is a
negative value)
to find distance from a speed-time graph simply find the area under the graph. It maybe a triangle ( ½ X base X height)
or a rectangle (l X W)
TICKER TAPE TIMER
pg 119
Equally spaced dots means constant speed, spaces between dots increasing means constant acceleration. Spaces
between dots decreasing means constant deceleration.
To find constant speed, start for 1 dot and count 10 intervals note the distance. The time taken to make 10 dot intervals
is a ten-tick which is 0.02 seconds. So speed = dist/time
To find constant acceleration find V by taking the last strip length and dividing it by 0.02 s, then find U by taking the first
strip length and dividing it by 0.02 seconds, then find t by counting the intervals between the first and last strips and
times that number by 0.02 seconds. Then substitute values into the equation for acceleration (V-U)/t.
NEWTON’S FIRST LAW OF MOTION: a body at rest stays at rest or if moving it continues to move with uniform velocity,
unless an external force makes it behave differently. Pg 130
Inertia: the mass of a body is a measure of its inertia it is the tendency of an object to remain at rest or in its state of
constant motion.
NEWTON’S SECOND LAW OF MOTION: the acceleration of an object is directly proportional to the applied force if its
mass is constant and indirectly proportional to its mass if the force is constant. F= mXa note that F is resultant or net
force on the object. Any object moving with constant velocity has a net zero force acting on it. Any accelerating object
has an unbalanced force acting on it.
MOMENTUM: Mass X velocity (kg m/s) pg 135
NEWTON’S THIRD LAW OF MOTION: for every action there is an equal and opposite reaction.