Physics Definitions

what is newtons first law

An object at rest stays at rest and an object in motion stays in motion with the same velocity and in the same direction unless acted upon by an unbalanced force.

what is newtons second law

When a resultant/net force acts on an object, the object will accelerate in the direction of the force at an acceleration directly proportional to the force and inversely proportional to the mass of the object

what is newtons third law

When one body exerts a force on a second body, the second body exerts a force of equal magnitude in the opposite direction on the first body

what is newtons law of universal gravitation

Each particle in the universe attracts every other particle with a gravitational force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres

Definition of weight

is the gravitational force the Earth exerts on any object on or near its surface.

Definition of frictional force

Frictional force is the force that opposes the motion of an object in contact with a surface and it acts parallel to the surface the object is in contact with.

velocity

rate of change of displacement with respect to time

Instantaneous speed is…

the speed of an object at a particular moment in time.

For total displacement …

only the initial and final positions are important.

For total distance …

you must determine the total path length.

Definition of inertia

The tendency of an object to resist a change in its state of motion

Definition of resultant force

A single force that has the same effect as all the forces acting on an object

A passenger is seated in a fast moving-taxi when the taxi driver suddenly slams on the breaks. Use your knowledge of Newton's laws to explain why the passenger moves forward when breaks are applied.

The passenger and taxi move with the same velocity before breaks are applied. When breaks are applied, the net force acts on the taxi (and not the passenger). Due to inertia the passenger continues to move forward.

Explain why wearing a seatbelt is a safety measure for occupants of a vehicle.

The occupant moving forward exerts a force on the seat belt. By Newton's third law, the seat belt exerts an equal force in the opposite direction to prevent the occupant from moving forward

definition of normal force

normal force is the force which a surface exerts on an object in contact with it and which is perpendicular to the surface.

definition of static frictional force

static frictional force is the force that opposes the tendency of motion of a stationary object relative to a surface

if a crate lies on a rough plane at an angle of 25 degrees, and the mass of the crate increases, will the crate begin to slide (yes or no)? Explain.

No. both the parallel component of the gravitational force and maximum static frictional force increase by the same magnitude

Definition of weightlessness

The sensation experienced when all contact forces are removed

What is the difference between the mass and weight of an object

Mass is the amount of matter contained in the body. Weight is the force with which the Earth attracts a body

Why is the following statement incorrect: "an astronaut orbiting earth experiences weightlessness because they are beyond the pull of earth's gravity"

The gravitational force exerted by the Earth still exists in orbit. Astronauts experience weightlessness because the only force acting on them is the gravitational force.

What is Coulomb’s law?

The magnitude of the electrostatic force exerted by one point

charge (Q1) on another point charge (Q2) is directly proportional to the product of

the magnitudes of the charges and inversely proportional to the square of the

distance (r) between them:

what is an electric field

electric field as a region of space in which an electric charge experiences a

force. The direction of the electric field at a point is the direction that a positive test

charge would move if placed at that point.

Define electric field at a point:

The electric field at a point is the electrostatic force

experienced per unit positive charge placed at that point.

What is Ohm’s law

the current through a conductor is directly proportional to the voltage across it and inversely proportional to its resistance, provided the temperature is kept constant

What is Faradays law of electromagnetic induction

a changing magnetic field induces an electromotive force (EMF), or voltage, in a conductor. The magnitude of this induced EMF is directly proportional to the rate of change of the magnetic flux through the conductor.

What is Lenz’s law

an induced electric current will flow in a direction that opposes the change in magnetic flux that produced it

Definition of momentum

1. Momentum is the product of an object’s mass and its velocity

Definition of linear momentum

The Linear Momentum of an object is equal to the product of the object's mass and its velocity

Law of conservation of momentum

The total linear momentum in a closed system is constant in magnitude and direction

What is kinetic energy

the energy an object possesses because it is motion

Elastic collisions

Ek of closed system is conserved. Ek(before) = Ek(after)

Inelastic collisions

total Ek of the objects in the system decreases. Ek(before) does NOT= Ek(after)

Define an inelastic collision

An inelastic collision is a collision between two objects in which the momentum of the system remains constant, but total kinetic energy does not remain constant.

Define an isolated system

An isolated system is a system on which the net force is zero

State the principle of conservation of linear momentum

The total linear momentum of an isolated system remains constant.

define an internal force

an interna force is a force exerted between an object within a system and another object in the same system

define an elastic collision

an elastic collision is a collision between two objects in which total momentum remains constant and the total kinetic energy remains constant