Motion in nature

 

At the end of this lesson, the students should be able to:

• Define force and explain its nature

• Identify, explain and distinguish between various types of force.

• List the types of  motion in a given environment 

• Classify a list of familiar motion into random, rotational, oscillatory and translational motion;  

• Identify for a given motion the two bodies between which there is a relative separation 

WEEK 4

TOPIC: Motion in nature

SUB – TOPIC

• Definition, type, causes, practical examples and effects

• Circular motion, centripetal and centrifugal forces

FORCE

This is simply referred to as the agency responsible for the change. The change in position of bodies with respect to a frame of reference with respect to time is caused by the force acting on such bodies. Forces only occur as a result of interaction between bodies. Without interaction, there will be no force. So force is that agency that changes or tend to change the state of a body at rest or at uniform motion along a straight line.

Mechanics is a branch of physics that deals with the study of force and its effects on bodies in the universe.

TYPE OF FORCE (elementary categorization)

1. Contact force

2. Force field (or Non-contact or distance force)

CONTACT FORCES

These are forces on bodies that are in contact with one another. Examples are:

• Frictional forces

• Tensional forces

• Normal forces

• Air resistance forces and

• Applied forces.

FORCE FIELD (NON-CONTACT OR DISTANCE FORCES)

These are those types of forces that occur when the two objects that are interacting do not have bodily contact with each other. Examples are:

• Gravitational force 

• Electric force

• Magnetic force

MEASUREMENT OF FORCE        

The standard unit (SI) of measurement of force is the Newton. A Newton is shortened as an "N."

1 N = 1kgm/s².

CLASSWORK

In the universe, there are four fundamental types of forces, mention and explain them with examples.

ASSIGNMENT

Explain the following force fields or non-contact forces:

1. Gravitational force

2. Electric force, and 

3. Magnetic force

MOTION

Motion is the change in position of an object with time. The main cause of motion is force.

TYPES OF MOTION

1. Linear or translational motion

2. Circular motion or rotational motion

3. Oscillatory or vibratory motion

4. Random motion

TYPES OF MOTION AND THEIR EXAMPLES

We can distinguish between four types of motion – 

(i) Random motion: this is the motion in which a body moves irregularly with no preferred direction e.g. Brownian motion, motion feathers in the air, the motion of smoke in the air etc.

(ii) Translational motion: This is the motion in which every point in a moving body remains fixed in relation to other points e.g. the linear motion of a car on a straight road, a bee flying from one flower to another etc.

(iii) Rotational motion or circular motion: this a kind of motion where every point in a body moves in circles, e.g. circular or rotational motion of fan blade, merry-go-round motion of children etc. 

(iv) Oscillatory or vibratory motion: in which a body moves to and fro, reversing its direction, and returning regularly to its position e.g. the motion of a pendulum bob, vibration of loaded spiral spring etc.

CLASSWORK

Give two instances where any the types of motion could be combined and explain them

ASSIGNMENT

What is the relative motion of a body with respect to a frame of reference?

RELATIVE MOTION

The relative motion of body A with respect to another body B is the motion of A from B. B is the frame of reference. In general, all motion involves the separation of an object relative to an observer (or point of reference).

i.e. VAB = VB - VA

CLASSWORK

Give five examples of motions which involve more than one type of motion 

ASSIGNMENT

What do you understand by relative motion?