Physical Science Unit 10

Newton’s First law is called Law of Inertia - Objects at rest will remain at rest, an object in motion will remain in constant motion unless and unbalanced force acts upon it.

• Inertia - The tendency of objects to remain in motion or stay at rest or an object “wants” to keep doing what its doing. INERTIA DEPENDS ONLY ON MASS

• Momentum - Is inertia of motion or how hard it is to stop and object p(momentum) = mass x velocity

• Conservation of momentum law - State that momentum (energy) is not lost but transferred from one object to another

Newton’s Second Law - The relationship of force, mass and acceleration. Force (Newtons) = Mass (Kg) x Acceleration (m/s²) to Solve for mass the equations is M=F/A & to Solve for Acceleration the equation is A=F/M

• A example of N-2 - Why do smaller less massive cars get better mileage? (more miles for every gallon) - Smaller cars have less mass so they require less force to accelerate than larger cars.

Newton’s 3rd Law: All forces come in pairs, For every action, there is an equal & opposite reaction.

• A example of N-3 - Rockets, Action of rocket is the rocket pushes fuel downward, the Reaction: fuel pushes the rocket upward

Gravity - Is the attractive force between all objects in the universe, Gravity is produced by all objects that have mas, Gravity accelerates objects on Earth at 9.9m/s/s, Gravity is a weak universal force Only noticeable with massive object, Strength of gravity depends on 2 factors Mass (Density) & Distance

• Measuring Gravity - Weight: measures the force of gravity (Units - Newtons or pounds) Formula for weight, Weight = mass x gravity(9.8m/s²), Weight can vary according to location not mass. the closer you are to the center of the Earth strong the force. So if you were at the beach or mountain top you would weigh a little less on the beach, close to earth’s core

• Newton’s UNIVERSAL LAW OF GRAVITY and his 3 laws of motion allowed him to

1. Prove that the planets elliptical orbits were resultant because of result from gravity

2. Calculate the mass of each planet

3. Calculate the flattening of the Earth at the poles

4. Determine that gravitational pull of the Sun and Moon create the Earth’s tides

• All objects in the universe attract each other with the force of gravity, The force of gravity is related to the masses of the object and their distance, This means the behavior of an object can be predicted

• The real reason that objects fall at different speeds is due to Air resistance or fluid friction in the absence of air a , free fall a bowling ball & a feather would reach ground at the same time

• Terminal Velocity: is the maximum speed of a falling object is reached when air friction = gravity, Results in balanced forces (N-3), How does it effect acceleration? - Once the force are balanced there are no change to falling object, continue falling constant speed. Less massive object will accelerate faster than more massive objects “light” objects (f=ma) actually fall faster than heavy object.

Example Questions

• Imagine a place in the mosmos far from all gravitational & frictional influence. Suppose that you visit that place and throw a rock. The rock will (gradually stop or contine in motion ) because : Lack of air resistance & inertia

• What will happen to the astronaut: Newton's 3rd law will go in the opposite direction