Motion:
A body is said to be in motion if it changes its position continuously with respect to a fixed point in its surroundings.
Rest:
A body is said to be at rest if it does not changes its position with respect to a fixed point in its surroundings.
Types of Motion:
Translatory/Linear motion:
a) Rectilinear motion: If the body moves in a straight line, its motion is rectilinear motion.
Example: A car moving along a straight road.
b) Curvilinear motion: If the body moves along a curved line, its motion is curvilinear motion
Example: A car turning on a round about.
Circular Motion:
It is the motion of a body in a circular path around a fixed point or a fixed axis.
a) Revolution: If the body as a whole moves round in a circular path, the motion is known as revolution.
Example: Motion of the Earth around the Sun, The motion of a stone tied to a string and whirled in a circle.
b) Rotation: If the body moves without changing its position from one place to another, its motion is called rotation.
Example: Motion of the blades of a fan, a spinning top, or a merry-go-round.
Oscillatory Motion:
To and fro motion of a body about a fixed point is called oscillatory motion.
Example: Motion of a pendulum, motion of swing.
Repetitive Motion:
If a same motion occurs again and again, it is said to be repetitive motion.
Example: The beating of a drum, revolution and rotation of earth, swinging of arms while walking.
Periodic Motion & Non- Periodic Motion:
a) Periodic Motion: A repetitive motion which repeats itself after a fixed interval of time is called the periodic motion.
Example: Oscillation of a pendulum, revolution of the Earth around the Sun, vibration of a stretched wire.
b) Non-periodic Motion: A repetitive motion which repeats itself but not at fixed interval of time is called the non-periodic motion.
Example: Swinging of arms while walking, heart beat.
Speed: Distance covered by an object in unit time is called as the speed of the object.
SI unit of speed - meter/second
speed= Distance/Time
Average Speed: When speed of a body is continuously changing the speed of whole journey is represented by average speed.
Average Speed= Total distance/Total time
Uniform Motion:
If the speed of an object moving along a straight line remains constant, its motion is said to be uniform.
Non-Uniform Motion:
If the speed of an object moving along a straight line keeps changing, its motion is said to be non-uniform.
Simple Pendulum: A simple pendulum consists of a small metallic ball suspended from a rigid stand by a light and inextensible thread. The metallic ball is called the bob of the pendulum.
Oscillation: The to and fro motion of a pendulum about its mean position.
Time period: Time taken to complete one oscillation.
SI unit-second
Frequency: Number of oscillations in one second is called frequency.
SI unit of frequency – hertz (Hz)
How our ancestor measure time?
For measuring time our ancestors used sundials, water clocks and sand clocks.
Name the device use to measure speed of vehicle
Speedometer
Name the device use to measure distance travelled by the vehicle
Odometer
Describe various steps to construct Distance-Time graph.
We can make the graph by following the steps given below:
1. Draw two perpendicular lines to represent the two axes and mark them as OX and OY.
2. Decide the quantity to be shown along the x-axis and that to be shown along the y-axis. In our case we show the time along the x-axis and the distance along the y-axis.
3. Choose a scale to represent the distance and another to represent the time on the graph.
4. Mark values for the time and the distance on the respective axes according to the scale you have chosen.
5. Now you have to mark the points on the graph paper to represent each set of values for distance and time
6. Join all the points on the graph. This is the d-t graph for the motion of the vehicle.
7. If the d-t graph is a straight line, it indicates that the object is moving with a constant speed. However, if the speed of the object keeps changing, the graph can be of any shape.
How can we choose a suitable scale? Explain giving example.
We should keep the following points in mind while choosing the most suitable scale for drawing a graph:
1. The difference between the highest and the lowest values of each quantity.
2. The intermediate values of each quantity, so that with the scale chosen it is convenient to mark the values on the graph, and
3. To utilise the maximum part of the paper on which the graph is to be drawn.
Suppose that we have a graph paper of size 25 cm× 25 cm and we have to accommodate following data:
A body is said to be in motion if it changes its position continuously with respect to a fixed point in its surroundings.
Rest:
A body is said to be at rest if it does not changes its position with respect to a fixed point in its surroundings.
Types of Motion:
Translatory/Linear motion:
a) Rectilinear motion: If the body moves in a straight line, its motion is rectilinear motion.
Example: A car moving along a straight road.
b) Curvilinear motion: If the body moves along a curved line, its motion is curvilinear motion
Example: A car turning on a round about.
Circular Motion:
It is the motion of a body in a circular path around a fixed point or a fixed axis.
a) Revolution: If the body as a whole moves round in a circular path, the motion is known as revolution.
Example: Motion of the Earth around the Sun, The motion of a stone tied to a string and whirled in a circle.
b) Rotation: If the body moves without changing its position from one place to another, its motion is called rotation.
Example: Motion of the blades of a fan, a spinning top, or a merry-go-round.
Oscillatory Motion:
To and fro motion of a body about a fixed point is called oscillatory motion.
Example: Motion of a pendulum, motion of swing.
Repetitive Motion:
If a same motion occurs again and again, it is said to be repetitive motion.
Example: The beating of a drum, revolution and rotation of earth, swinging of arms while walking.
Periodic Motion & Non- Periodic Motion:
a) Periodic Motion: A repetitive motion which repeats itself after a fixed interval of time is called the periodic motion.
Example: Oscillation of a pendulum, revolution of the Earth around the Sun, vibration of a stretched wire.
b) Non-periodic Motion: A repetitive motion which repeats itself but not at fixed interval of time is called the non-periodic motion.
Example: Swinging of arms while walking, heart beat.
Speed: Distance covered by an object in unit time is called as the speed of the object.
SI unit of speed - meter/second
speed= Distance/Time
Average Speed: When speed of a body is continuously changing the speed of whole journey is represented by average speed.
Average Speed= Total distance/Total time
Uniform Motion:
If the speed of an object moving along a straight line remains constant, its motion is said to be uniform.
Non-Uniform Motion:
If the speed of an object moving along a straight line keeps changing, its motion is said to be non-uniform.
Simple Pendulum: A simple pendulum consists of a small metallic ball suspended from a rigid stand by a light and inextensible thread. The metallic ball is called the bob of the pendulum.
Oscillation: The to and fro motion of a pendulum about its mean position.
Time period: Time taken to complete one oscillation.
SI unit-second
Frequency: Number of oscillations in one second is called frequency.
SI unit of frequency – hertz (Hz)
How our ancestor measure time?
For measuring time our ancestors used sundials, water clocks and sand clocks.
Name the device use to measure speed of vehicle
Speedometer
Name the device use to measure distance travelled by the vehicle
Odometer
Describe various steps to construct Distance-Time graph.
We can make the graph by following the steps given below:
1. Draw two perpendicular lines to represent the two axes and mark them as OX and OY.
2. Decide the quantity to be shown along the x-axis and that to be shown along the y-axis. In our case we show the time along the x-axis and the distance along the y-axis.
3. Choose a scale to represent the distance and another to represent the time on the graph.
4. Mark values for the time and the distance on the respective axes according to the scale you have chosen.
5. Now you have to mark the points on the graph paper to represent each set of values for distance and time
6. Join all the points on the graph. This is the d-t graph for the motion of the vehicle.
7. If the d-t graph is a straight line, it indicates that the object is moving with a constant speed. However, if the speed of the object keeps changing, the graph can be of any shape.
How can we choose a suitable scale? Explain giving example.
We should keep the following points in mind while choosing the most suitable scale for drawing a graph:
1. The difference between the highest and the lowest values of each quantity.
2. The intermediate values of each quantity, so that with the scale chosen it is convenient to mark the values on the graph, and
3. To utilise the maximum part of the paper on which the graph is to be drawn.
Suppose that we have a graph paper of size 25 cm× 25 cm and we have to accommodate following data:
One of the scales will be:
Distance: 5 km = 1 cm, and
Time: 6 min = 1 cm
Using this scale we can draw a distance-time graph as given below:
Importance of distance-time graph
Graph used to describe the motion of a body by illustrating the relationship between the distance that it travels and the time taken. The slope of d-t graph at any point is the body's speed at that point.
1. If d-t graph is parallel to time axis, the body is at rest.
2. If the slope is constant (the graph is a straight line), the body has uniform or constant speed;
The slope of the line determines the speed; the higher the slope the greater the speed
3. If the slope varies (the graph is curved), speed of body is
not constant (In this graph speed is increasing)
3. If the slope varies (the graph is curved), speed of body is
not constant (In this graph speed is increasing)
