Seneca - Newtons Laws Flashcards
Newton’s second law
A resultant force causes an acceleration.The acceleration can be calculated with this equation.Resultant force (F) = mass (m) x acceleration (a).This is Newton’s 2nd Law.
Resultant forces - total force acting upon an object. Resultant forces may cause an acceleration or change in an objects motion of unbalanced.
Newton’s first law
Newton’s 1st Law says that the velocity of an object will only change if a resultant force is acting on the object.
Stationary object - no resultant force = stay stationary
If an object is moving and there is no resultant force acting on it, the object will continue moving in the same direction at the same speed.This means that the object will continue moving at the same velocity.This also means that the velocity of an object will only change if a resultant force is acting on the object.
Newton’s third law
Newton’s Third Law says that: whenever 2 objects interact, the forces that they exert on (apply to) each other are equal and opposite.If one object exerts (applies) a force on another object, then the other object must be exerting (applying) a force back.
(Momentum)
Momentum equation
Momentum = Mass x velocity
Change in momentum = force x time
Change in momentum = (mass x final velocity) - (mass x initial velocity).
EXAM QUESTION
using ideas about momentum, explain how a rocket is launched.
The rocket starts at rest and has no momentum.The rocket pushes the fuel out of the bottom of the rocket. The fuel has gained momentum in the direction of the ground (earth).The conservation of momentum means that the rest of the rocket must gain momentum in the opposite direction. This propels (pushes) the rocket into the sky.
Force and momentum equation
(IMPORTANT TO DESCRIBE COLLISIONS AND INCREASING TIME OF COLLISION AFFECT ON FORCE)
Force = change in momentum ÷ change in time.In other words, force is equal to the rate of change of momentum.
How do car safety features work ? Crumple zone, safety bag, seat belts.
These features reduce injuries to the people in the car by absorbing energy when they change shape. (Combines f=ma and a = v-u ÷t
When a crash takes place, there is a certain change in momentum.The force felt by the person is the change in momentum divided by the time taken.Safety features of a car increase the time taken for the momentum to change.Therefore reducing the force felt by the person in the crash.
Why is a large force exerted in a car crash
If an object which has a lot of momentum is made to stop suddenly, then a large force is required because of the change in momentum.
