Module 3 Definitions and Statements Flashcards
Define simple harmonic motion.
Force/acceleration is proportional to displacement (from equilibrium position)
(Resultant force) force/acceleration is (always) towards equilibrium position
State the principle of moments
(When an object is in equilibrium the) sum of clockwise moments (about a point) = sum of anticlockwise moments (about the same point)
Define velocity.
velocity = rate of change of displacement
Define acceleration.
acceleration = rate of change of velocity
Define thinking distance.
The distance travelled (by the car) from when the driver sees a problem and the brakes are applied
Define work done by a force.
work done = force x distance moved in direction of force
Explain the term drift velocity
Drift velocity: average mean/net/overall velocity of electron along wire
Define the newton.
Force is 1 N when a 1 kg mass has an acceleration of 1 m s–2
Define a couple
Two equal but opposite forces
Define the torque of a couple
torque = one of the forces x perpendicular distance between the forces
Define density
density = mass/volume or ‘density is mass per
(unit) volume’
Define braking distance of a car.
The distance travelled (by the car) whilst the brakes are applied and the car stops
State two conditions necessary for an object to be in equilibrium
Net / total / resultant force = 0
Net / total torque / moment = 0
Define moment of a force
moment = force x perpendicular distance from point / pivot
Define centre of gravity
The point where the weight (appears) to act
State the principle of conservation of energy.
Energy cannot be created or destroyed; it can only be transferred/transformed into other forms
or
The (total) energy of a system remains constant
or
(total) initial energy = (total) final energy (AW)
Define the Young modulus of a material.
Young modulus = stress/strain
As long as elastic limit is not exceeded
Define the watt.
1 J (of work done) per second
Define power
power = work done/ time
or energy/time
or ‘rate of work done’
State Hooke’s law
Extension is proportional to force (applied as long as the elastic limit is not exceeded)
Explain what is meant by plastic deformation.
Material is permanently deformed / longer when stress / force is removed
Define ultimate tensile strength of a material.
Maximum stress material can withstand (before
fracture)
Define the force constant of a spring.
force/extension or force per (unit) extension
State Hooke’s law for a material in the form of a wire and state the conditions under
which this law applies.
the force (needed to stretch a spring is directly) is proportional to the extension (of the spring from its natural length) up to the limit of proportionally
Explain what is meant by the elastic limit of the wire
the maximum amount that a material can be stretched (by a force) and still return to its original length when the force is removed
State the meaning of
tensile stress
stretching) force (applied) per unit cross-sectional area
State the meaning of tensile strain
extension (produced) per unit length
State in words Newton’s second law of motion
(Resultant) force (acting on an object) is (directly) proportional to the rate of change of momentum (and occurs in the same direction)
Define the impulse of a force
Force x time for which the force acts / duration of collision
Define linear momentum.
(linear momentum =) mass x velocity
State the principle of conservation of linear momentum
Total momentum is constant/conserved for a closed system/provided no external forces
Explain what is meant by an inelastic collision.
Some loss of kinetic energy during collision
State Newton’s second and third laws of motion.
Force is proportional to the rate of change of momentum
When one body exerts a force on another the other body exerts an equal (in magnitude) and opposite (in direction) force on the first body
