Mechanics Flashcards
Define speed
distance travelled per unit time
vector
a quantity of both direction and magnitude
scalar
scalar quantities have magnitudes only
velocity
change in displacement per unit time
acceleration
change in velocity per unit time
The Newton
the force that causes a mass of 1kg to accelerate at 1m/s SQUARED
moment
force x perpendicular distance from the pivot
The turning effect caused by a force on a pivoted object.
principle of moments
for rotational equilibrium, the sum of the clockwise moments about a pivot equals the sum of the anticlockwise moments about the pivot
torque of a couple
one of the forces × perpendicular distance between the forces
(The product of two forces in opposite directions, and equal distance from the pivot)
an object in equilibrium
sum of all forces acting on the object is zero;
clockwise moments on the object equal anticlockwise moments about the pivot
centre of gravity
point where all the weight (or mass) of a body appears to act
density
mass / volume
pressure
force normal to surface / area
work done
force × distance moved in the direction of the force
the Joule
the work done when 1 Newton acts over a distance of 1 metre
power
work done / time OR the rate at which work is done/energy is transferred
(1 watt = 1 joule / second)
thinking distance
distance travelled from when driver detects hazard to when driver applies brakes
braking distance
distance travelled after the brakes have been applied until vehicle stops
gravitational potential energy
mass × gravitational field strength × height
kinetic energy
½ × mass × speed2
Average speed
The overall distance travelled divided by time taken
Instantaneous speed
The speed of an object at a particular instant in time
Conservation of energy
A principle stating that the total energy of an isolated system remains constant, regardless of changes within the system.
Displacement
The distance travelled in a particular direction from the origin.
