momentum Flashcards
What is kinetics?
Is the study of forces that cause motion
What are Newtons 3 laws of motion?
Three laws that form the basis of conventional or Newtonian Me-
chanics. The laws can be remembered by the acronym IN-MO-RE:
1) first law of Inertia,
An object at rest will remain at rest, and an object in motion will remain in motion with a constant velocity unless acted on by a net external force.
running uniformly then trip over a massive rock which causes me to fall.
2) second law of Momentum/acceleration
the acceleration of an object is directly proportional to the net force acting upon the object and inversely proportional to the object’s mass.
The second law also states that the change in
momentum will be in the direction of the resultant force.
strongman Apollons wheel a force is applied to accelerate or move the object
3) third law for every Reaction.
For every action, there is an equal and opposite reaction.
vertical jump force applied into the ground by muscles and ground applies force back trampolines do the opposite
refers to impulse
When two bodies collide head-on and then continue to travel collectively in the original direction of motion of one of the bodies, what factor determines the direction of the motion after the collision?
The relative momentum of the 2 bodies
P=mv
The work done by the external forces causes a change in energy of the object
W = ∆ E=J
Work W = ΔE = Fd W
OR
W = change in KE + change in PE
OR
W = (½ mv2) + (mag ∙h)
-This expression is derived from the work-energy relationships principle, which states that the work done on an object is equal to the change in its kinetic energy plus the change in its potential energy.
If a greater amount of work done there is a greater change in PE?
or
If a larger force is exerted or a larger force over a longer
distance, we can increase the amount of work done?
True, why? because a greater work done is proportional to the change in KE
True, because both are increasing the applied force the distance over which the force is applied can lead to an increase in the amount of work done on an object.
Shod vs barefoot? which one requires more energy?
why is the shoe more energy-demanding?
-shoe has more mass and has to act against gravity
-accelerating with an extra mass e.g the shoe
if a shoe weights= 100g
speed of leg swing =10 m/s
step length or distance is= 2m (21000 steps)
what is the PE or work done against gravity?
PE= 0.1 kg x 9.81 m/s2 x 0.2 m x 21100 steps
PE=41140j of work
KE=1/2mv^2
KE=0.05x10^2
KE=5m/s2 x21100 steps
W=105500 J or 250.9Kcal
Newtons second law of motion?
Key: everything is related to Newton’s second law (F=MA), but we are adding time (t)
Momentum – the quantity of motion. Greek for “movement”.
Depends on 2 factors:
1. How much “stuff” is moving (mass/ F)
2. How fast the “stuff” is moving (velocity/ A)
Conservation of energy is defined as?
Conservation of collision: for a collision occurring between object 1 and object 2 in an isolated system, the total momentum of the two objects before the collision is equal to the total momentum of the two objects after the collision.
what is impulse?
The change in momentum experienced by a body under the action
of a force is equal to the impulse of the resultant force.
The effect of a force acting over some time.
what does the law of conservation of energy state?
Law of conservation of mechanical energy – when gravity is the only acting external force, a body’s mechanical energy (which is equal to difference between the PE and KE) remains constant (only occurs in human movement when the object is a projectile and if we neglect air resistance) – 2 formulas to represent this:
what are the 2 formulas that can be used to calculate Conservation of enegy?
- PE + KE = 0
- PE = -KE
When gravity is the only acting external force, a body’s
mechanical energy remains constant___________
PE + KE = Constant
This only occurs in human movement when the object is a projectile and we neglect air resistance
4 stages of PE and KE for a projectile:
- At the point of release – PE is 0, KE is maximal
- Travelling upwards – PE increasing, KE decreasing
- At apex – PE is maximal, KE is 0
- During downward flight – travelling upwards reversed
- At the bottom – same as at the point of release
explain an example of when a object starts from the bottom how does it effect PE and KE?
The ball in the hand or on the ground
PE=0
KE=Maximums
Ball thrown up
PE= increasing
KE=Decreasing
the ball being thrown up to height (h)
PE= increasing
KE=0
When the ball reaches it max (h)
PE= At its Maxuimuim
KE=0
explain an example of when a object travels downwards ?
its is opposite
PE decreases downwards
KE increases downwards
at the bottom
KE is at its maximin
PE is 0
