Mechanics Flashcards
SI units, projectiles, moments, Newtons laws, momentum
Give two examples or scalar and vector quantities
Scalar - speed, time, distance
Vector - velocity, displacement, acceleration
Rules for scale diagrams
Use biggest scale possible for the paper to reduce uncertainty
Consider positioning on paper to maximise space
Observation of projectiles
Stationary objects dropped or shot along from the same height will hit the ground at the same time due to equal forces acting down on them
How to calculate distance a projectile landed from start point
-use SUVAT to find time projectile was in the air for (either from highest point to lowest or lowest to highest)
-use a vector triangle to work out the horizontal component of the force (if needed)
- use the time calculated to work out distance traveled using distance = speed x time
- if the object is rising and then falling, double the time before finding the distance
How does an object reach terminal velocity
The object is accelerating due to either gravity or thrust from the object
As speed increases, so does drag (air resistance)
Eventually drag=force so the resultant force is 0 and the object is at terminal velocity
What is a moment?
Units?
Moment is the turning effect of a force (also called torque)
Units are Nm
what is a couple?
a pair of forces that are qual in magnitude and opposite in direction acting parallel but not on the same line (eg. steering wheel)
state the principle of moments
for an object in equilibrium, the sum of the clockwise moments is equal to the sum of the anticlockwise moments about any pivot
state Newton’s first law
an object will remain at rest or travelling in a straight line at constant velocity provided there is no resultant/net force
state Newton’s second law
the rate of change of momentum of a body is directly proportional to the net force creating it
(if mass is constant, sum of forces = ma)
state Newton’s third law
if object A exerts a force on object B, the object B exerts a force on object A that is equal in magnitude, opposite in direction and of the same type.
what is the conservation of momentum?
in any direction, with no external forces, the total momentum of a system remains constant.
(sum of initial momentum = sum of final momentum)
linear momentum equation
(including units)
momentum = mass x velocity
kgms^-1 = kg x ms^-1
what is impulse?
change in momentum
how to calculate impulse?
force x change in time
force x change in time = change in mv
