Conceptual Physics--Test Review Chp 2 to 9

Scalar

A quantity in physics such as Mass,Time,Volume

Vector Quantity

A quantity in physics, such as force, that has both magnitude and direction.

Mechanical Equilibrium

A state wherein no physical changes occur. it is a state of steadiness. whenever a net force on an object is 0, the object is said to be in mechanical equilibrium.

Watt

A watt is a measure of power equal to one joule of work per second. The standard metric unit of power is the Watt. As is implied by the equation for power, a unit of power is equivalent to a unit of work divided by a unit of time. Thus, a Watt is equivalent to a Joule/second. For historical reasons, the horsepower is occasionally used to describe the power delivered by a machine. One horsepower is equivalent to approximately 750 Watts.

Air restistance

Air resistance is a force that is caused by air. The force acts in the opposite direction to an object moving through the air.

Two Types of motion

Aristotle, the famous Greek scientist, studied motion and divided it into two types: NATURAL MOTION and VIOLENT

Fluids

Both liquids and gasses are called fluids because they flow.

Chemical energy

Chemical energy is available in molecules for release in a chemical reaction; a form of potential energy.

Complex machines

Complex machines are when two or more simple machines are put together. Example: wheel barrow combines wheel and axle with a lever.

Constant velocity

Constant velocity means both constant speed and constant direction. Constant direction is a straight line; the objects path does not curve.

Constant force

For a constant force, an increase in the area of contact will result in a decrease in the pressure.

Friction

Friction is the name given to the force that acts between materials that touch as they move past each other.

Friction

Friction is the resistance that one surface or object encounters when moving over another.

Galileo and friction

Galileo argued that only when friction is present - as it usually is- is a force needed to keep an object moving. eg. experiments with rolling balls.

Gravitational potential energy

Gravitational energy is stored by objects due to their position above Earth's surface. Gravitational potential energy is the energy stored in an object as the result of its vertical position or height. The energy is stored as the result of the gravitational attraction of the Earth for the object.

Changing velocity

If either the speed or the direction or both change, than the velocity is changing. A car has three controls that are used to change velocity; the gas pedal, the brake, the steering wheel.

inelastic collisions

In an inelastic collision, the total momentum of the two bodies remains the same, but some of the initial kinetic energy is transformed into heat energy internal to the bodies, used up in deforming the bodies, or radiated away in some other fashion.

inversely

Inversely means two values change in opposite directions.

Tension

Is the upward force action on a suspended object. (Stretching force)., (physics) a stress that produces an elongation of an elastic physical body

Kinetic energy

Kinetic energy is the energy of motion. The kinetic energy of an object is the energy it possesses because of its motion. Kinetic energy = 1/2 mass X velocity 2(squared)

momentum

Momentum is the quantity of motion of a moving body, measured as a product of its mass and velocity.

Newton's First Law (law of inertia) of Motion

Newton's first law states that every object continues in a state of rest, or of uniform speed in a straight line unless acted on by a non net zero force.

Force causes acceleration (Newton's 2nd Law)

Newton's second law provides the explanation for the behavior of objects upon which the forces do not balance. The law states that unbalanced forces cause objects to accelerate with an acceleration that is directly proportional to the net force and inversely proportional to the mass.

Static Equilibrium

Objects at rest are said to be in static equilibrium

Objects at rest.

Objects in a state of rest tend to remain at rest. Only a force will change that rest.

Objects in motion

Once an object is moving in a force free environment, it will move in a straight line indefinitely. Forces are needed to overcome any friction that may be present and to set objects in motion initially.

Potential energy

Potential energy is the stored energy of position possessed by an object. Potential energy has the "potential to be used". This energy is not being used currently.

Power

Power is the rate at which work is done. It is the work/time ratio. Mathematically, it is computed using the following equation. Power = Work / time or P = W / t

Reaction force

Reaction force is force acting in the opposite direction. (Newton's 3rd Law)

Scalar Quantity

Scalar quantity is a quantity that can be described by MAGNITUDE ONLY and has no direction. time, area, and volume are scalar quantities

Speed

Speed is how fast an object is moving. You can calculate the speed of an object by dividing the distance by time. Speed = distance/time

Law of Conservation of Energy

The Law of Conservation of Energy states that energy cannot be created or destroyed, but only changed from one form into another or transferred from one object to another.

The Law of Conservation of Momentum

The Law of Conservation of Momentum states that for a collision occurring between object 1 and object 2 in an isolated system, the total momentum of the two objects before the collision is equal to the total momentum of the two objects after the collision. That is, the momentum lost by object 1 is equal to the momentum gained by object 2.

Average speed

The average speed is the total distance covered by the time. avg speed= total instance recorded/ time interval

Net Force

The combination of all the forces that act on an object. A net force on an object changes its motion.

Efficiency

The efficiency of a machine is the ratio of useful energy output to total energy output in any machine, some energy is transformed into atomic or molecular energy- making the machine warmer - this wasted energy is dissipated as heat. efficiency= useful work output/total work output

Weight

The force on a body due to the gravitational attraction of another body; Is the downward force caused by gravitational pull.

Horse and cart problem

The horse and cart problem is an application of Newton's Third Law, which says: For every action, there is an equal and opposite reaction. If A exerts a force on B, then B will exert an equal and opposite force on A.

Law of Inertia

The law of inertia states that objects in motion remain in motion if no unbalanced forces act on them. (note) objects move with the earth and with moving vehicles.

Mass - a measure of inertia

The more mass an object has, the greater its inertia and the more force it takes to change its state of motion. MASS is NOT volume. MASS is NOT weight.

Inertia

The property of a body to resist changes to its state of motion is called inertia.

Instantaneous speed.

The speed at any instant is called the instantaneous speed.

Stable Equilibrium

The state of an object balanced so that any small displacement or rotation raises it's center of gravity.

Resultant

The sum of two or more vectors is called the resultant.

Support force

The upward force that balances the weight of an object on a surface; Also called a normal Force for an object at rest on a horizontal surface, the support force must equal the objects weight. we say the upward support force is positive and the downward weight is negative. the two forces add to 0.

Force and mass

The weight of an object is the force of gravity on the object and may be defined as the mass times the acceleration of gravity, w = mg. Since the weight is a force, its SI unit is the newton. Density is mass/volume

action = reaction

These two forces are called action and reaction forces and are the subject of Newton's third law of motion. Formally stated, Newton's third law is: For every action, there is an equal and opposite reaction.

Velocity

VELOCITY is NOT speed. Velocity is speed in a given direction. Speed is a description is how fast an object moves. VELOCITY IS HOW FAST AND IN WHAT DIRECTION AN OBJECT IS MOVING.

Work

When a force acts upon an object to cause a displacement of the object, it is said that WORK was done upon the object. There are three key ingredients to work - force, displacement, and cause. In order for a force to qualify as having done work on an object, there must be a displacement and the force must cause the displacement. Work = Force x Distance

Change in speed

When the direction is not changing, acceleration may be expressed as the rate which speed changes. Speed and velocity are measured in units of distance per time. Since acceleration is the change in velocity or speed per time interval, its units are those of speed per time. acceleration=change in speed/time

Relative

When we describe the motion of one object with respect to another, we say that the object is moving RELATIVE to the object.

Collisions

collisions can either be elastic, meaning they conserve both momentum and kinetic energy, or inelastic, meaning they conserve momentum but not kinetic energy. An inelastic collision is sometimes also called a plastic collision.

Kilograms

the SI unit of mass, equivalent to the international standard kept at Sèvres near Paris (approximately 2.205 lb).

Pressure

the amount of force per unit of area is called pressure p= f/area of application

Mass resists acceleration

∑ F = m a For a constant force, an increase in the mass will result in a decrease in the acceleration (inversely proportional)

A force is needed to . . .

A force is needed to change an object's state of motion.

Free body diagram

A free body diagram is a diagram showing all the forces acting on an object; A diagram used to isolate a body from its environment, showing all external forces acting upon it.

Joule

A joule is a unit of work or energy equal to the work done by a force of one newton acting through a distance of one meter.

Interaction

A mutual action between objects where each object exerts an equal and opposite force on the other.

Dynamic Equilibrium

Objects moving at constant speed in a straight line path are said to be in dynamic equilibrium. both static and dynamic equilibrium are examples of mechanical equilibrium.

Dynamic Equilibrium

Objects moving at constant speed in a straight-line path.

Speed versus time

On a speed versus time graph, the slope represents speed per time, or acceleration. The "'curve" on this graph shows that the points form a straight line. the straightness of the curve indicates LINEAR relationship between speed and time.

Distance versus time

This graph has a curved line, which shows that the relationship between distance traveled and time is non-linear.

Decreasing momentum

..., Decrease velocity, mass, force, time applied or all of them.

Bouncing

..., impulses are greater when an object bounces

momentum vectors

..., the sum of the momentum vectors is the same before and after a collision.

newton

1 kg weighs 10 newtons. the SI unit of force is the newton. In most parts of the world the measure of matter is commonly expressed in units of mass.If you know the mass of something in KG and want its weight in newtons at earth's surface, multiply the number of kg by 10. If you know the weight in newtons, divide by 10 and you will have the mass in kg.

elastic collisions

A perfectly elastic collision is defined as one in which there is no loss of kinetic energy in the collision. An inelastic collision is one in which part of the kinetic energy is changed to some other form of energy in the collision.

Change in direction

Acceleration is defined as the rate of change in velocity rather than speed. Acceleration, like velocity, is a vector quantity because it is directional. If we change speed, direction, or both we change velocity and we accelerate.

Newton's Second Law of Motion

Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) The greater the amount of force needed (to accelerate the object.) acceleration = netforce/mass

Acceleration

Acceleration is the rate at which velocity is changing. You can calculate the acceleration of an object by dividing the change in its velocity by time. acceleration = change in velocity/time interval.

Action force

Action force is force acting in one direction. Reaction force is force acting in the opposite direction.(Newton's 3rd Law)

Increasing momentum

Also called linear momentum. Mechanics. a quantity expressing the motion of a body or system, equal to the product of the mass of a body and its velocity, and for a system equal to the vector sum of the products of mass and velocity of each particle in the system.

Vector

An arrow whose length represents the magnitude of a quantity and whose direction represents the direction of the quantity.

Inclined planes

An inclined plane is the simplest of simple machines and is nothing more than a flat surface tilted at an angle. The trade- off is that in order to decrease the effort force, the length of the ramp must be increased.

Force

An influence that tends to accelerate an object; a push or pull exerted on a object; a push or pull measured in Newtons. A vector quantity. State of motion: at rest, or moving in a uniformly line.

Equilibrium Rule

An object is in mechanical equilibrium whenever the Net Force on the object is ZERO; For any body in mechanical equilibrium, the vector sum of the forces on it are zero- that is, ∑F=0.

Motion is relative

An object is moving if its position RELATIVE to a fixed point is changing.

Elastic potential energy

Elastic potential energy due to the deformation of an elastic object, such as the stretching or compressing of a string. Elastic potential energy is the energy stored in elastic materials as the result of their stretching or compressing. Elastic potential energy can be stored in rubber bands, bungee chords, trampolines, springs, an arrow drawn into a bow, etc. The amount of elastic potential energy stored in such a device is related to the amount of stretch of the device - the more stretch, the more stored energy.

Energy

Energy is the capacity to do work. Energy is the capacity of a physical system to perform work. Energy exists in several forms such as heat, kinetic or mechanical energy, light, potential energy, electrical, or other forms.

Impulse changes momentum

Force against its motion for a given period of time. The more momentum that an object has, the harder that it is to stop. Thus, it would require a greater amount of force or a longer amount of time or both to bring such an object to a halt. As the force acts upon the object for a given amount of time, the object's velocity is changed; and hence, the object's momentum is changed.

Newton's Third Law of Motion

Formally stated, Newton's third law is: For every action, there is an equal and opposite reaction. The statement means that in every interaction, there is a pair of forces acting on the two interacting objects.

Lift

LIFT: AN UPWARD FORCE THAT OPPOSES THE DOWNWARD PULL OF GRAVITY. An aircraft in flight experiences an upward lift force, as well as the thrust of the engine, the force of its own weight, and a drag force. The lift force arises because the speed at which the displaced air moves over the top of the airfoil (and over the top of the attached boundary layer) is greater than the speed at which it moves over the bottom and because the pressure acting on the airfoil from below is therefore greater than the pressure from above.

Mass

Mass is the quantity of material in an object MASS IS A MEASURE OF THE INERTIA that an object exhibits in response in any effort to start it, stop it, or otherwise change its state of motion.

Parallelogram rule

To find the resultant of two nonparallel vectors, construct a parallelogram wherein the two vectors are adjacent sides. The diagonal of the parallelogram shows the resultant.

Work - energy theorum

Work-energy theorem. The work-energy theorem states that the work done on an object by the net force is equal to the change in its kinetic energy. The energy associated with the work done by the net force does not disappear after the net force is removed (or becomes zero), it is transformed into the Kinetic Energy of the body. We call this the Work-Energy Theorem.