An Introduction To Motion
Distance
Distance is the total path covered by the object in the given interval of time.
Displacement is the shortest path covered by the moving object within the given interval of your time .
Distance=Speed×Time.
Unit of distance is usually measured in units of length like metres, kilometres etc.
Introduction to Motion
An object is claimed to be in motion if it changes its position with reference to time. Eg: A car moving on a road.
An object is claimed to be at rest if the thing doesn't change its position with time. Eg: A person standing on the ground.
Basics of Standard Units
Units and their Standardization
The standard unit of distance is in metres.
The standard unit of your time is in seconds (s).
The standard unit of speed can be measured in metre per second (m/s).
Basics of Motion and Its Types
Types of Motion
Types of motion are generally divided into parts -
Rectilinear / Translatory motion: When a body occupies a line , without changing its direction, then the body is claimed to possess translatory/rectilinear motion. Eg: A car moving on a straight road.
Circular Motion: When a body moves within the shape of a circle with a few fixed points and a hard and fast radius, then the body is claimed to be in circular motion. Eg: Motion of planets around the sun.
Period / Oscillatory Motion: When the motion of a body repeats after fixed intervals of your time , then the body is claimed to within the periodic/oscillatory motion. Eg: The movement/motion of a pendulum that is to and fro.
Periodic or Oscillatory Motion
Periodic or oscillatory motion is that the motion during which a body repeats its motion after fixed intervals of your time .
Eg: The movement/motion of a pendulum that is to and fro, Motion of a car in a circular path, Motion of planets around the sun.
Oscillations of a Simple Pendulum
When the bob of an easy pendulum moves from its mean position B to A and back to B again, then from B to C and back to B again, the pendulum is said to complete 1 oscillation.
In the case of the simple pendulum, the time period is the total time taken by the pendulum to complete one oscillation.
Time and Speed
Speed (Average Speed)
Speed is the total distance travelled by the object in a given interval of time.
Speed = Distance travelled/time taken
Unit of speed is generally measured in metre per second(m/s), kilometre per hour(km/h).
Uniform and Non-Uniform Motion
1. Uniform Motion: When an object moving along a line moves with a continuing speed, then the thing is claimed to be in uniform motion. Eg: A car moving in a straight line with a constant speed.
2. Non-uniform Motion: When an object moving along a line changes its speed with reference to time, then the thing is claimed to be in uniform motion. Eg: The motion of a train.
Measurement of Time
Unit of your time is usually measured in seconds, minutes, hours. The time period is the total time taken by an object to complete one oscillation.
Units of Time
Unit of your time is usually measured in seconds, minutes, hours.
Units of Speed
Speed = Distance travelled in the total time interval.
Unit of speed is generally measured in meters per second (m/s) and km/h( kilometre per hour).
Speedometer and Odometer
Speedometer records the speed of the vehicle directly in kilometers per hour (km/h).
An odometer measures the space moved by the vehicle directly in kilometres(km).
Visualizing Motion
Distance-Time Graph
Distance-time graph is the graph plotted between the distance( in y-axis) and time ( in x-axis).
The slope of a distance-time graph gives the speed of an object.
FAQs on Motion and Time
1. What is motion and how do we determine if an object is moving?
An object is said to be in motion when its position changes with respect to time and a fixed reference point. For example, a car is in motion relative to a tree on the roadside. If the object's position does not change with time, it is considered to be at rest.
2. What are the main types of motion described in Class 7 Physics?
The primary types of motion studied are:
- Rectilinear motion: Movement along a straight line, like a sprinter running on a 100m track.
- Circular motion: Movement along a circular path, like the tip of a clock's hand.
- Periodic or Oscillatory motion: Motion that repeats itself after a fixed interval of time, like a child on a swing or the to-and-fro movement of a simple pendulum.
3. How do you calculate the speed of a moving object?
The speed of an object is calculated by dividing the total distance it travels by the total time taken to cover that distance. The formula is Speed = Total Distance Covered / Total Time Taken. The standard unit for speed is metres per second (m/s), although it is also commonly expressed in kilometres per hour (km/h).
4. What is the difference between uniform and non-uniform motion?
Uniform motion occurs when an object moving along a straight line travels at a constant speed, covering equal distances in equal intervals of time. In contrast, non-uniform motion occurs when an object's speed changes over time, meaning it covers unequal distances in equal intervals of time. A car moving on a busy street is a good example of non-uniform motion.
5. Why are standard units for measuring time and distance important?
Standard units, like the second for time and the metre for distance, are crucial for ensuring consistency and universal understanding in science and daily life. Without them, measurements would be subjective and vary from person to person, making it impossible to compare data, replicate experiments, or conduct fair trade.
6. How does a simple pendulum's motion help in measuring time?
A simple pendulum exhibits periodic motion, meaning it takes a fixed amount of time to complete one full swing, or oscillation. This fixed duration is called its time period. Early clocks, like grandfather clocks, used this predictable and consistent time period of a pendulum as a basis for measuring seconds, minutes, and hours accurately.
7. What information can we learn from a distance-time graph?
A distance-time graph provides a visual summary of an object's journey. From the graph, you can determine:
- The distance an object has travelled at any point in time.
- The speed of the object, which is calculated from the slope (or steepness) of the line.
- Whether the object is in uniform motion (a straight, sloped line), at rest (a horizontal line), or in non-uniform motion (a curved line).
8. How can a distance-time graph show if a car is stopped or moving at a constant speed?
On a distance-time graph, a horizontal line parallel to the time axis indicates that the distance is not changing. This means the car is stopped or at rest. A straight line slanting upwards shows that the car is covering equal distances in equal time intervals, which signifies it is moving at a constant (uniform) speed.
9. What do the speedometer and odometer in a car measure?
A speedometer is an instrument that measures and displays the vehicle's instantaneous speed—its speed at that exact moment—usually in kilometres per hour (km/h). An odometer is another instrument that records the total distance the vehicle has travelled since it was manufactured.
10. Can an object have more than one type of motion at the same time? Provide an example.
Yes, an object can exhibit multiple types of motion simultaneously. For example, a wheel of a moving bicycle has rotational motion (as it spins around its axle) and rectilinear motion (as it moves forward in a straight line with the bicycle). Similarly, the Earth has both rotational and revolutionary motion.
