Phys Sci Chapter 2

motion

the act or process of changing position relative to some reference during a period of time

speed

a ratio of distance per unit of time

speed formula

speed= distance/time

speed units

meters per second (m/s) or kilometers per hour (kmh)

velocity vs speed

velocity is a vector unit while speed is a scalar unit

vector

has both magnitude and direction

scalar quantity

only has magnitude

3 ways the motion of a object can be changed

changing speed, direction, or both

acceleration formula

acceleration= change in velocity/elapsed time

acceleration unit in physical science (usually)

m/s²

true or false: acceleration is a vector quantity

true

force

a push or pull that is capable of changing the motion of an object

net force

the sum of all forces acting on an object

True or false: forces are vector quantities

true

four fundamental forces

gravitational, electromagnetic, weak nuclear force, strong nuclear force

gravitational force

attractive forces between all objects in the universe

electromagnetic force

responsible for structure of atoms, chemical change, electricity, and magnetism

weak nuclear force

involved in nuclear reactions

strong nuclear force

close-range force that holds the nucleus together

free fall

the only force acting on an object is gravity, air resistance is neglected

projectile motion

movement of an object in the vertical direction and the horizontal direction

Newton’s first law of motion

Every object retains its state of rest or its state of uniform straight-line motion unless acted upon by an unbalanced force. The First Law is affectionately referred to as the Law of Inertia

Newton’s second law of motion

The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to the mass of the object.

Mass is the amount of _____ in an object, weight is the measure of the _________ on an object

matter, gravitational pull

Mass is measured in _______; weight is measured in ___________

g or kg, pounds or Newtons

A ______ is used to measure mass; a ________ is used to measure weight (force)

balance, scale

Mass will _________ regardless of gravitational pull; your mass will be the same on earth as on the moon, your weight ______

stay the same, will not

mass

can also be defined as the ability of an object to resist motion; the greater the mass, the greater the inertia

Newton's Second Law is abbreviated as _______

F = ma

Force is measured in a unit called a _______ A Newton is equal to a kg m/s2.

Newton

A Newton is equal to a _____

kg m/s2

formula for weight

w= mg (g represents the acceleration due to gravity)

on Earth, what number is g in the weight formula

9.8 m/s²

Newton’s Third Law of Motion

Whenever two objects interact, the force exerted on one object is equal in strength and opposite in direction to the force exerted on the other object. This law is often called the action-reaction law.

momentum

the product of the mass of an object and its velocity

momentum formula

momentum= mass x velocity

Law of Conservation of Momentum

the total momentum of a group of interacting objects remains the same in the absence of external forces

Impulse

the product of the force and time of application; causes a change in momentum p = Ft

How far away was a lightning strike if thunder was heard 5.00 seconds after seeing the flash? Assume that sound traveled at 350.0 m/s during the storm.

1750m

What is the acceleration of a car that moves from rest to 15.0 m/s in 10.0 s?

1.5 m/s²

What is the average speed of a truck that makes a 160-kilometer trip in 2.0 hours?

80 km/hr

What force will give a 40.0 kg grocery cart an acceleration of 2.4 m/s²?

96N

An unbalanced force of 18N will give an object an acceleration of 3 m/s². What force will give this very same object an acceleration of 10 m/s²?

60N

What is the weight of a 70.0 kg person?

686N

What is the momentum of a 100 kg football player who is moving at 6 m/s?

600 kg m/s

A car weighing 13,720 N is speeding down a highway with a velocity of 92 km/h. What is the momentum of the car?

36,966 kg m/s

A 15 g bullet is fired with a velocity of 200 m/s from a 6kg rifle. What is the recoil velocity of the rifle?

-0.5 m/s

A net force of 5,000 N accelerates a car from rest to 90 km/h in 5.0s. What is the mass of the car? What is the weight of the car?

9800 N