mechanics Flashcards
what is meant by terminal velocity
when the forces acting on the falling object become balanced, the acceleration becomes zero and the object is moving at maximum velocity
what is meant by friction
a resistance to motion between
an object and a surface or
an object moving through a fluid.
Friction is a force that acts in the opposite direction to the movement
what is Newton’s 3rd law?
for each force experienced by an object, the object exerts an equal and opposite force
what is Newton’s 2nd law?
F=ma
the resultant force is directly proportional to the rate of change of momentum and acts in the same direction
What is Newton’s first law?
an object will remain in its current state of motion, unless acted on by a resultant force.
An object requires a resultant force to be able to accelerate
what is the equation for momentum?
momentum = mass x velocity
p=mv
as well as impulse, what can also be described as the change of momentum?
force x time
what is impulse?
the change in momentum
what are the units for impulse and momentum?
Ns and Kgm/s
what does the area underneath a force-time graph represent?
impulse/change in momentum
what is the rate of work done equal to?
power
what is efficiency?
useful output/
total output
what is meant by the principle of conservation of energy?
energy cannot be created or destroyed,
only transferred into other forms of energy
therefore, total energy in a closed system will always remain the same
what is the difference between mass and weight?
mass is scalar and is not dependent on the gravity acting upon it
weight is a vector and depends on the gravitational field strength
what is the principle of moments?
for an object in equilibrium,
the sum of clockwise moments (about a pivot) is equal to the sum of anti clockwise moments
what does it mean for an object to be in equilibrium?
it is not accelerating
it is either stationary or moving at a constant velocity
what is a moment and what is its equation?
a turning force:
force x perpendicular distance from the point to the line of action of the force
what is meant by a couple?
a pair of equal and opposite coplanar forces
what is meant by centre of mass?
the point through which all the mass of an object acts, for a uniform object the centre of mass is the centre of the object
what is the change in displacement per unit of time?
velocity
what is free fall?
where an object experiences an acceleration of g
what is lift?
an upward force which acts on an objects travelling in a fluid
what causes lift?
an object creating a change in the direction of fluid flow, and it acts perpendicular to the direction of fluid flow
What are the properties of a vector quantity?
A vector quantity is one that has both a magnitude and a direction.
Examples include velocity, displacement and acceleration.
what is an inelastic collision?
A collision in which the total kinetic energy of the system before the collision is not equal to the kinetic energy of the system after the collision.
How do you find velocity on a displacement-time graph?
velocity is found by measuring the gradient of a tangent to a displacement-time graph
what is the difference between mass and weight?
mass is scalar and is not dependant on the gravity acting upon it
weight is a vector and depends on the gravitational field strength
W=mg
What does it mean for an object to be in equilibrium?
not accelerating, so either
stationary
or moving at a constant velocity
what is a couple?
a pair of equal and opposite coplanar forces
where is the centre of mass for a uniform object?
the centre of the object
what is the area under a velocity-time graph?
displacement travelled
what is the area under an acceleration-time graph?
velocity
as speed increases, air resistance …
increases
(proportional to the square of the speed)
What is the vertical acceleration in projectile motion?
gravitational field strength, g
what happens at terminal velocity?
the forces acting on the falling object become balanced so the acceleration becomes zero
the object is moving at maximum velocity
Is linear momentum conserved only in elastic collisions?
no, linear momentum is always conserved
what can be described as the rate of change of momentum?
force
what are two equations for impulse?
I = FΔt = Δmv
