Motion

MOTION

What is Motion?

Motion is the act or process of moving.

Any object that changes in position is in motion, wheter you are riding a bicycle, running or even walking, you are in motion.

Some Motion Terms

Scalar .vs. vectorDistance & DisplacementVelocity & SpeedAccelerationUniform motion

Motion can be described in terms of measured quantities:

SCALAR QUANTITY - completely described by the size or

magnitude

(e.g. volume, mass, time)

VECTOR QUANTITY- described by the magnitude or size of the

distance traveled as well as its direction. (e.g. velocity, acceleration)

Distance & Displacement

Distance is the actual distance traveled.

Displacement depends only on Start & Finish line. Shortest distance between two points.

Displacement is the distance traveled, in a certain direction.

Distance & Displacement

SPEEDRate of movement of an object

from one place to another at a period of time.

distance (d)S = time (t)

Example:

A runner runs 100 meters in 7 seconds. What is his speed?

Given: d= 100 m t= 7 sec.Speed = ?

(d)S = (t)

= 100 m 7 sec.

= 14.29 m/sec.

VELOCITYRate of change in the position of

an object as it moves in a particular direction.

distance (d)Velocity (u) = time (t)

*with direction

Example:A car travels 30 kilometers east in one

hour. Calculate the velocity of the car.

(d)Velocity = (t)

30 km = 1 hr

= 30 km/hr east

AVERAGE VELOCITY

Change in displacement per change in time.

change in distance

Average Velocity (u) = change in time

= d2 – d1

t2-t1

Example:

Starting from rest an ambulance travels 50 km west for 1.5 hrs to pick up a patient. What is the average velocity of the ambulance?

Given: d1 = 0

d2 = 50 km

T1 = 0

T2 = 1.5 hrs

Average velocity = ?

Solution:

50 km – 0

u = 1.5 hrs – 0

= 50 km

1.5 hrs

= 33.33 kph

Instantaneous speed and velocity

Instantaneous speed is the speed of an object at any particular given instant while the instantaneous velocity shows the velocity of an object at one point.

ACCELERATIONRate of change in velocity over time due to

change in speed or/and direction.

An accelerating object is speeding up, slowing down, or changing the direction in which it is moving.

v a = t

*m/s/s

Average AccelerationRate at which velocity changes

divided by an elapsed time.

For example, if the velocity of a marble increases from 0 to 60 cm/s in 3 seconds. Its average acceleration would be 20 cm/s/s.

a = Vf - Vi

Tf – Ti

= 60cm/s – 0 3sec – 0

= 20 cm/s/s

ACCELERATION DUE TO GRAVITY

Is the acceleration for any object moving under the sole influence of gravity.

It is such an important quantity that physicist

have a special symbol to denote it – the symbol g.

All objects falling near the earth’s surface fall with a constant acceleration. The numerical value for this is accurately known as 9.8 m/s/s.

Two Dimensional Motion

PROJECTILE MOTION -- is the curved motion of an object that is objected into the air.

Projectile – is any object that is thrown projected into the air.

Trajectory – is the path taken by a

projectile.

UNIFORM CIRCULAR MOTIONCan be described as the motion of an

object in a circle at a constant speed. As an object moves in a circle it is constantly changing its direction. At all instances, the object is moving tangent to the circle.

CENTRIPETAL FORCE

Is the force directed toward the center of a circle

NEWTON’S LAW OF MOTION

First Law

“ An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force”

INERTIA

tendency of an object to resist any change in its motion

Inertia makes objects keep on doing whatever they are doing. Everything made of matter has inertia, even you.

NEWTON’S LAW OF MOTION

Second Law

“ The acceleration of an object depends directly upon the net force acting upon the subject and inversely upon the mass of the object”

1. A constant force produces a constant acceleration

2. Doubling the force will double the acceleration

3. Doubling the mass requires a force twice as large to achieve the same acceleration

F = m a

NEWTON’S LAW OF MOTION

Third Law

“ Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first”

Newton’s third law of motion states that an object experiences a force because it is interacting with some other object. The force that object A exerts on object B must be of the same magnitude but in the opposite direction as the force that object B exerts on object.

UNIVERSAL LAW OF GRAVITATION

“Every particle in the universe attracts every other particle in the universe with a force that depends on the product of the two particles' masses divided by the square of the distance between them”

Gravitational constant (G) X mass (m1) X mass (m2)

(F) = distance (d)2

Where:

G = 6.67 X 10 -11 Nm2 /kg2