Forces and motion Flashcards
methods of measuring g
Electromagnets and a trapdoor
Light gates
Recording object in free fall next to meter rule
Projectile motion
Vertical velocity changes due to acceleration of free fall
Horizontal velocity remains constant(no forces acting)
Total velocity is calculated by pythagorus
What is the velocity at the peak of a parabola?
Vertical velocity = 0, so total velocity = horizontal velocity
What are the four forces
The strong force
The weak force
Electrostatic
Gravitational
How do you find center of mass/gravity
A freely suspended object will come to rest with its center of gravity directly below the point of suspension
For multiple lines, center of mass is point of intersection
Factors affecting drag
speed (drag is proportional to speed ^2), shape, roughness/texture of object, density of fluid
Terminal velocity
The velocity at which weight = drag so object is no longer accelerating
Aerogel
The least dense solid in the world, with a density of 1.9 kgm^-3
Archimedes’ principle
The upthrust exerted on a body immersed in a fluid, whether fully submerged or partially, is equal to the weight of the fluid that the body displaces
Archimedes’ principle derrivation
force at top surface = hPgA
force at bottom surface =(h+x)PgA
Resultant force = upthrust = AxPg
Ax = volume
volume x density = mass
mass x g = weight
Derrivation of water pressure formula
p = F/A
p=(mg)/A
P(density)=m/v
p=(Pvg)/A
p=(P(lxwxh)g)/(lxw)
p=hPg
When will an object sink
When its weight is greater than upthrust (weight of liquid displaced)
This happens if object is more dense than the liquid
Forms of energy
Kinetic, gravitational potential, chemical, elastic potential, electrical potential, nuclear, radiant/electromagnetic, sound, internal(heat or thermal)
Derrivation of KE equation
F=ma
E=F x s = ma x s
s = (v² -u²)/2a
E = m a (v²-u²)/2a
u=0
E=mv²/2
Derrivation of gpe equation
W=f x s
force = weight = mg
distance = height
gpe = mgh
area under force extension graph
work done
what is the shape of a force extension graph for rubber and why
hysteresis loop
rubber consists of tangled long chain molecules. They are easily untangles but once straightened, need large forces to extend
tensile stress
force/cross sectional area
tensile strain
extension/original length
Young’s modulus
stress/strain
extrinsic
property of a material, not an object
elastic and inelastic collisions
both conserve momentum and energy, but perfectly elastic collisions conserve kinetic energy while inelastic collisions do not
how to investigate momentum
linear air tracks
trolleys with a light gate and data logger
why is Newton’s second law not F=ma
this only applies when mass is constant, which is not always the case
area under force-time graph
Impulse (=change in momentum = Ft)
