Class 7 Science Chapter 9 Important Question Answers - Motion and Time

Very Short Answer Type Questions

Q1: What is speed in the context of motion?
Ans: Speed is the distance covered by an object in a unit of time. It measures how fast or slow an object is moving.

Q2: Define average speed.
Ans: Average speed is the total distance covered by an object divided by the total time taken for the journey.

Q3: What is the basic unit of time?
Ans: The basic unit of time is the second (s).

Q4: Which unit is used to measure speed in the metric system?
Ans: Speed is measured in meters per second (m/s) in the metric system.

Q5: What is a speedometer, and what is its purpose?
Ans: A speedometer is an instrument used in vehicles to display the vehicle's speed. It shows how fast the vehicle is moving.

Q6: How are large speeds commonly measured?
Ans: Large speeds are commonly measured in kilometers per hour (km/h).

Q7: Define uniform motion.
Ans: Uniform motion refers to the motion of an object in a straight line at a constant speed, covering equal distances in equal intervals of time.

Q8: What is non-uniform motion?
Ans: Non-uniform motion is the motion in which the speed of an object varies, i.e., it does not move at a constant speed.

Q9: What is oscillation in the context of time?
Ans: Oscillation refers to the repeated back-and-forth or to-and-fro motion of an object around a central position.

Q10: How is the time period of a pendulum defined?
Ans: The time period of a pendulum is defined as the time it takes to complete one full oscillation.

Short Answer Type Questions

Q11: Explain the concept of speed and how it is calculated.
Ans: Speed is the measure of how fast or slow an object is moving. It is calculated by dividing the distance covered by the object by the time taken. The formula for speed is: Speed = Distance/Time.

Q12: Differentiate between uniform motion and non-uniform motion with examples.
Ans: Uniform motion is when an object moves in a straight line at a constant speed, covering equal distances in equal intervals of time. Example: A car moving on a straight road at a steady 60 km/h. Non-uniform motion is when the speed of an object varies during its motion. Example: A car slowing down as it approaches a traffic light.

Q13: What are the basic units for time and distance? How is speed measured?
Ans: The basic unit for time is the second (s), and the basic unit for distance is the meter (m). Speed is measured in meters per second (m/s) using the formula Speed = Distance/Time.

Q14: Describe the purpose and function of a speedometer and an odometer in vehicles.
Ans: A speedometer is an instrument that displays the vehicle's speed, allowing the driver to know how fast they are traveling. An odometer tracks the total distance covered by the vehicle over time, helping in mileage calculations and maintenance records.

Q15: Explain the concept of oscillation and provide an example.
Ans: Oscillation refers to the back-and-forth or to-and-fro motion of an object around a central position. An example is a swinging pendulum where the bob moves to one side, then to the other, repeatedly.

Q16: How do natural events and man-made structures help in measuring time?
Ans: Natural events like phases of the moon and man-made structures like sundials or the Jantar Mantar in Jaipur are used to measure time. For example, the position of the sun's shadow on a sundial indicates the time of day.

Q17: Define the time period of a pendulum and explain its significance.
Ans: The time period of a pendulum is the time it takes to complete one full oscillation. In pendulum clocks, the time period of the pendulum is constant, making them accurate timekeepers.

Q18: What are graphs, and why are they useful in representing data?
Ans: Graphs are pictorial representations of numerical data that help in better understanding and comparing information. They are useful because they provide a visual representation of data, making it easier to interpret and analyze.

Q19: Name and briefly describe the three types of graphs.
Ans: The three types of graphs are:

1. Bar graphs: These use horizontal or vertical bars to show numerical comparisons.
2. Pie charts: Circular graphs that represent relative percentages or shares of a whole.
3. Line graphs: Use lines to connect data points and show the variation of one quantity with respect to another.

Q20: Explain how the shape of a graph differs for a body in uniform motion, a body at rest, and a body in non-uniform motion.
Ans:

• Body in uniform motion: The graph is a straight line making an angle with the horizontal axis.
• Body at rest: The graph is a straight line along the X-axis, indicating zero speed.
• Body in non-uniform motion: The graph is not a straight line, and the speed varies.