Laws Governing Motion Chapter 2

Question 1

Velocity

Answer 1

• The speed in a particular direction of a moving body.
• Speed combined with its direction of motion
• Involves both magnitude and direction.

Question 2

The First Law of Motion

Answer 2

Every object at rest, or in uniform motion, will remain in that state of motion unless compelled to do otherwise by forces acting upon it.

Question 3

Uniform Motion

Answer 3

• Motion at a constant speed in a straight line.

* The same as unaccelerated motion.

Question 4

State of Uniform Motion

Answer 4

• The condition of an object when no unbalanced forces act upon it.
• A state of motion always refers to being at rest or in uniform motion.

Question 5

Force

Answer 5

A push or a pull, exerted by one object on another.

Question 6

A state of rest

Answer 6

• A state of rest is uniform motion with zero speed.

* An object at rest remains at rest if it is left alone.

Question 7

Acceleration

Answer 7

• A change in an object’s velocity.
• Like velocity acceleration also has magnitude and direction.
• Acceleration can increase speed, decrease speed or change the direction of an object’s motion.
• ** Rate of change of velocity per unit time, or change of velocity divided by the time required for the change.
• Acceleration is caused by a force.
• The converse is not true, if a force is present it does not have to cause an acceleration. If another forces balances it out, there will be a net force of zero and no resulting change in the state of motion.

Question 8

Centripetal acceleration

Answer 8

• Means: Toward a center.

* Acceleration at a right angle to an object’s velocity will change to object’s direction without changing its speed

Question 9

Velocity vs Acceleration

Answer 9

• Velocity is distance in a particular direction covered in a certain time.
• It is measured in “meters per second”, “miles per hour…”
Acceleration is the rate at which speed or direction changes, and has a measurement like, “meters per second per second (meters per second squared), or “miles per hour per second”.

Question 10

The Second Law of Motion

Answer 10

• Force = mass x acceleration
• F = ma
• a = F/m
• a = F/m Shows that the acceleration of an object is directly proportional to the (net) force on it and inversely proportional to its mass.

Question 11

Net Force

Answer 11

• The sum of all the forces (present) acting on an object.
• Forces pushing in the same direction add together to increase net force.
• Forces acting in opposite directions add against each other, decreasing net force.

Question 12

Unbalanced forces

Answer 12

• The total of any force that is not cancelled out by other, competing forces.
• The portion of the total force that is unopposed by other forces and so will cause an acceleration. An unbalanced force means that the net force is NOT zero.
• Unbalanced forces are acting whenever an object moves faster, slower, changes direction, or experiences any combination of speed and direction change.
• The direction of the acceleration is always in the direction of the unbalanced force.

Question 13

Mass

Answer 13

• The characteristic of a body which determines how much it accelerates when a force is applied.
• The property of an object that determines how much it will accelerate in response to an applied force is called mass.
• Mass does not depend on location.

Question 14

Weight

Answer 14

• A measure of the force of gravity pulling on an object.

* Weight does change with location.

Question 15

Strength of Forces

Answer 15

• Measured in pounds (lb) in the English Imperial system and in units of newtons (N) in the metric system.
• 1 N = 1/4 lb.
• Stronger forces produce greater accelerations.

Question 16

Inertia

Answer 16

• The property that is suppose to move an object from rest, or keep it moving once it has started.
• Newton’s first law is sometimes referred to as, “Law of inertia”.
• But no force or agent is needed to keep an object moving in uniform motion; it just moves.
• Inertia is a qualitative term for mass - although mass does not keep an object in motion, it does represent the difficulty of getting the object to change its state of motion.

Question 17

Qualitative vs Quantitative

Answer 17

• Newton’s First Law of Motion is a qualitative statement about motion and the presence or absence of force.
• Newton’s Second Law is quantitative. It says exactly HOW MUCH the motion of an object of mass (m) changes when acted on by a force of magnitude (F). referring to information based in quantifiable data —as opposed to qualitative information which deals with apparent qualities.

Question 18

Newton’s Third Law of Motion

Answer 18

• All forces result from interactions between pairs of objects, each object exerting a force on the other. The two resulting forces have the same strength and act in exactly opposite directions.

• Forces occur only when TWO things (objects) interact with each other. A single sided force cannot exist.
• Nothing in isolation can exert a force on itself.
• This is a rule about forces.

Question 19

Slug

Answer 19

Used to measure the unit of mass in the English imperial system.