section 3 - mechanics Flashcards
what is a moment?
force x perpendicular direction from axis to line of action of force.
momentum equation?
mass x change in velocity.
state newton’s first law.
an object remains and rest or in constant motion unless acted on by a resultant force.
state newtons second law.
F = ma (the resultant force is proportional to the rate of change of momentum)
what is an alternate form of momentum equation?
F = ma (ma = momentum)
what is an impulse?
time in which a force (F) acts.
what is the same as an impulse?
impulse = rate of change of momentum.
if a ball rebounds of a wall in an elastic collision, what is the momentum of the ball after the collision?
-2mu
no change in speed so v=u
in an elastic collision, if a ball bounces off a wall at angle cos(), what is the change in momentum of the ball?
-2muCos()
state newtons third law.
when two objects interact they exert an equal and opposite force on each other.
what happens to momentum in all collision?
momentum is ALWAYS conserved (if no external forces are acting).
what is the difference between an elastic and inelastic collision?
KE is conserved in an elastic collision, not conserved in inelastic.
energy cannot be ……………… or …………………….
created , destroyed
what does the area under a force/distance graph equal?
work done.
work done equation?
work done = force x distance moved in direction of force.
if you turn through the angle do you use Cos() or Sine()
Cos()
spring constant equation?
F = K x change in length.
what does the are under a force/time graph show?
change in momentum.
what does the area under a force/extension graph show?
work done to stretch a spring.
work done to stretch a spring equation?
work done = 0.5 x force x change in length.
when a lift is accelerating upwards, what is the tension in the cable?
T = mg + ma (T = w + (F to accelerate))
what are the three main forces involved with accelerating a lift?
weight, force to accelerate, tension in cable.
does newtons first law apply to forces acting on the same object or different objects in contact?
different objects, same force.
when a lift is accelerating downwards, what is the tension in the cable?
T = mg - ma ( negative acceleration) (T = w + F to accelerate)
pulley problem equation?
mg - mg = (M + m) x a.
accelerate at the same rate). (both equal result force
how to calculate resultant force from x2 forces?
F2 - F1
what is the gradient of a distance/time graph?
speed.
what is the area under distance/time graph?
total distance travelled.
what is the difference between distance and displacement?
displacement has a direction and magnitude.
