kinematics + energy Flashcards
define speed
distance travelled per unit time
define displacement
straight line distance of an object from a fixed reference point
define velocity
rate of change of displacement
define acceleration
rate of change of velocity
kinematics equations
v = u + at
v^2 = u^2 + 2as
s = (u+v)/t
s = ut + 1/2at^2
derivations from s/t graph
gradient = velocity
derivations from v/t graph
gradient = acceleration
area under = change in displacement
derivations from a/t graph
area under = change in velocity
what can negative acceleration mean?
- object is slowing down in the positive direction
- object is speeding up in the negative direction
define energy
the capacity to do work
formula for GPE
mgh (kg x g ms-2 x m)
formula for KE
1/2 mv^2 (kg x ms-1)
mechanical energy
sum of kinetic and gravitational potential energy in an object used to do work
initial ME = final ME
or initial ME = final ME + work done
define law of conservation of energy
energy cannot be created or destroyed, only converted from one form to another
formula for work done
force x distance moved in the direction of the force (Nm)
define power
rate of doing work
formula for power (W)
total work done / total time
force x velocity when velocity is constant
formula for efficiency
useful energy output / total energy output x 100%
