Resumén física

Physics Summary
1º Term:
The mathematical quantities which are used to describe the motion of objects can be divided into two categories. The quantity is either a vector or a scalar. These two categories can be distinguished from one another by their distinct definitions:
• Scalars are quantities which are fully described by a magnitude (or numerical value) alone.
• Vectors arequantities which are fully described by both a magnitude and a direction.
Distance and displacement are two quantities which may seem to mean the same thing yet have distinctly different definitions and meanings.
• Distance is a scalar quantity which refers to "how much ground an object has covered" during its motion.
• Displacement is a vector quantity which refers to "how far out of placean object is"; it is the object's overall change in position.
VECTORS: a vector which is perpendicular to a surface
How much and direction

Resultant: 5

a2+b2+c2

Vector quantity is a quantity that has both magnitude and direction in space:

• Displacement

• Velocity

• Acceleration

• Force

Resultant is the sum of the combined effect of 2vectors quantities.

6N 4N = 10N

6N/4N = 10N

6ms-1 10ms-1 = 4ms-1

6ms-1 10ms-1 = 4ms-1

Velocity-Time
The relation between velocity and time is a simple one during constantly accelerated, straight-line motion. The longer the acceleration is, the greater the change in velocity. If after a time velocity increases by a certain amount, after twice that time it shouldincrease by twice that amount. Change in velocity is directly proportional to time when acceleration is constant. If an object already started with a certain velocity, then its new velocity would be the old velocity plus this change.

V = s/t
V = V2+ a * t
V= V2 + 2 * a * s

Displacement-Time
The displacement of a moving object is directly proportional to both velocity and time.Acceleration compounds this simple situation. Now the velocity is also directly proportional to time. "Displacement is directly proportional to time and directly proportional to velocity, which is directly proportional to time". Time is a factor twice, making displacement proportional to the square of time. A car accelerating for two seconds would cover four times the distance of a car accelerating for onlyone second (22 = 4). A car accelerating for three seconds would cover nine times the distance (32 = 9). This example only works when initial velocity is zero.

S = v * t

T= V/t

Velocity-Displacement
Change in displacement is proportional to the change in the square of velocity when acceleration is constant. This statement is particularly important for driving safety. When you double thespeed of a car, it takes four times the distance to stop it. Triple the speed and you'll need nine times the distance. Like the previous relationships, it also depends on initial velocity.

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FREE FALL:

V= 0 ms-1

U = 15 ms-1

V = U – g * t

0 = 15 – 10 * t

10 * t = 15

T = 1,3 s

Hmax= (1,5) (1,5) – ½ (10) (1,5)2 = 11,25 m

H = U * t + ½ * g *t2H = height

V= U + g * t T = time g = acceleration of gravity (10 ms-2)

V2 = U + 2 * g * h V= final velocity

U= Initial velocity

Newton's First Law

A body in motion remains in motion unless it is acted on by an external force.If the body is at rest it remains at rest.

E F = 0

Newton's Second Law

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

E F = m * a

Newton's Third Law of Motion

Newton's third law applies to pairs of bodies. If a body A exerts a force on a body B, then body B exerts an equal and opposite force on body...