C4 Flashcards
Mass of object
physical property - depends on amount of matter object contains
Net force
Net force acting on an object makes object accelerate in the direction of the force
equation relating force, mass and acc
F=ma
mass vs weight
mass remains constant everywhere but weight changes depending on location
equation relating w, m and g
W=mg
g on Earth
9.81 ms^-2
how to measure weight
using a newtonmeter, use on different planets
Centre of mass
Centre of mass of an object - point through object which any externally applied force produces straight line motion but no rotation
Centre of gravity
A single point throguh which resultant force of whole object acts through
Weight
Gravitational force acting on an object through its centre of mass
Friction
The force that arises when two surfaces rub against each other
Drag
The resistive force on an object travelling through a fluid e.g. air or water (like friction)
Tension
the force within a stretched cable / rope/ object
upthrust
an upward buoyancy force acting on an object when it is in a fluid
normal contact force
a force arising when one object rests against another object
Factors affecting magnitude of drag force
shape of object
roughness of object
density of object it is moving through
speed of object
common relationship between drag force and speed
drag force is directly proportional to speed 2
Terminal velocity
when drag force is equal to weight
acceleration is 0
investigating motion in a fluid practical
-drop a ball bearing into a fluid
to record velocity:
use motion sensor connected to a data logger
OR
use stopcock and ruler to determine velocity at regular intervals using v = s/t
-plot v-t graph and analyse results
