Forces and Momentum Flashcards
State Newton’s 1st law of motion
An object at rest remains at rest or in uniform motion unless acted on be a force
State Newton’s 2nd law of motion
The rate of change of momentum of an object is proportional to the resultant force on it. In other words, the resultant force is proportional to the change of momentum per second
Give the equation for the force applied to an object with changing momentum
F = d(mv)/dt = ma
N.b. F = ma only applies for an object with constant mass
Define the impulse of a force
the force x the time for which the force acts
Impulse = F∆t = ∆ma
What does the area under the line of a force-time graph represent
The change of momentum or the impulse of the force
Give the equation for acceleration of an object when given its initial and final velocity during a given time
a = (v-u)/t
Define the momentum of an object and give its units
mass x veocity
in kgm^s-1 or Ns
Give an equation for the force of an impact
Force of impact = Change in momentum / contact time
F = (mv - mu) / t
State Newton’s 3rd law of motion
When two objects interact, they exert equal and opposite forces on each other
State the Principle of Conservation of Momentum
For a system of interacting objects, the total momentum remains constant, provided no external resultant force acts on the system
If two identical objects collide elastically with each other at the same speed, what is the resultant velocity of each object and why?
The direction of each object will be reversed but be at the same original speed. This is because the momentum and kinetic energy of the system is always conserved in an elastic collision.
Define an elastic collision
An elastic collision is one where there is no loss in kinetic energy
Define a totally inelastic collision
A totally inelastic collision is one where the colliding objects stick together (coalesce)
Define a partially inelastic collision
A partially inelastic collision is where the colliding objects move apart but have less kinetic energy after the collision than before
What can always be said about the total momentum of a system that has exploded?
It always remains constant
