Chapter 7 Laws of motion and momentum Flashcards
What is newtons first law?
An object will remain at rest or continue moving with a constant velocity until acted on by an external force
What is newtons third law?
When two objects interact, they exert equal and opposite force on each other.
What are the 4 fundamental forces?
Gravitational, electromagnetic, strong and weak nuclear
What is the equation for momentum?
Momentum = mass x velocity
What is the unit for momentum?
kgms-1
What is the principle of conservation of momentum?
For a system of interacting objects, the total momentum in a specific direction remains constant, as long as no external forces act on the system. The momentum before and after a collision is the same.
Talk about the momentum of a gun and a bullet
The bullet and the gun have the same momentum but the mass of the gun is much larger so the velocity is smaller.
What is a perfectly elastic collision?
Kinetic energy is not transformed into other energies It is a collision where momentum, energy and kinetic energy are conserved
What is an inelastic collision?
Kinetic energy is transformed into other energies in the collision Momentum and total energy is conserved but kinetic energy is not conserved
What is newtons second law of motion?
The net force acting on an object is directly proportional to the rate of change of momentum and is in the same direction Force is proportional to the rate of change of momentum
What is the equation that links force and momentum?
Force = Change in momentum / Change in time
In terms of momentum, how do airbags work?
The force is reduced by increasing the time to change the momentum
Why is momentum conserved in collisions?
In a closed system the net forces on an object are zero. Net forces are proportional to the rate of change of momentum so the change in momentum is zero. So the momentum of objects must not change and momentum is always conserved
