Exercises: Time & Motion | Class 7 Oxford Science: Chapter Notes, Worksheets & Tests PDF Download

Objective Type Questions 

A water clock and a sand clock are two examples of ancient clocks.
Water clock and sand clock were used in ancient times to measure time.

Q.2. A sundial works only in the____________ (day/night). 

A sundial works only in the day.
Sundial uses the sun's position to tell the time and hence works only during daylight hours.

Q.3. In a pendulum, the greater the length of the string, the__________ (greater/lesser) is the time period.

In a pendulum, the greater the length of the string, the lesser is the time period.
The time period of a pendulum is directly proportional to the square root of its length. Therefore, greater the length of the string, the longer the time period. 

Q.4. The speed of an object is defined as the distance travelled by it in. ___________(One hour/unit time). 

The speed of an object is defined as the distance travelled by it in one hour.
Speed is defined as the distance travelled by an object per unit time, which is usually measured in meters per second or kilometers per hour.

Q.5. Average speed is measured in.____________(minutes per hour/ metre per second).

Average speed is measured in meters per second.
Average speed is calculated by dividing the total distance travelled by the total time taken. It is usually measured in meters per second or kilometers per hour.

B. Choose the correct option. 

Very Short Answer Type Questions 

Minutes, Seconds

Q.2. Time-measuring instruments in earlier times  _________ ___________

Sundial, Water clock

Q.3. Modern time-measuring instruments   _________ ___________

Quartz clock, Atomic clock

Q.4. Factors on which the time period of a pendulum depends  _________ ___________

Length of the pendulum, Acceleration due to gravity

Q.5. Factors on which the time period of a pendulum does not depend  _________ ___________

Mass of the pendulum, Amplitude of the swing.

Short Answer Type Questions 

Periodic motion is the motion that repeats itself after a fixed interval of time. The time taken for one complete cycle of the motion is called its time period.

Q.2. Name the following:
a. Instrument for measuring speed in an automobile
b. Instrument for measuring distance travelled in an automobile 

a. Instrument for measuring speed in an automobile is called a speedometer.

b. Instrument for measuring distance travelled in an automobile is called an odometer.

Q.3. What is the time period of a pendulum? 

The time period of a pendulum is the time taken by it to complete one oscillation, i.e., the time taken for it to swing from one extreme end to the other and come back to its initial position. It is usually measured in seconds.

Q.4. What is one oscillation of a pendulum? 

One oscillation of a pendulum is the movement of the pendulum from one extreme end to the other and back to its initial position. It is also known as one complete cycle of the pendulum's motion.

Q.5. What is average speed?

Average speed is the total distance travelled by an object divided by the total time taken to cover that distance. It is represented by the formula:

Average speed = Total distance travelled / Total time taken. It is usually expressed in km/h or m/s.

Long Answer Type Questions 

The measurement of time is important to us because it helps us to organize our daily activities and perform them in a timely manner. It also helps us to keep track of important events, appointments, and deadlines. In addition, time measurement is crucial in various fields such as science, engineering, and transportation.

Q.2. How did people in earlier days measure time using the following?
a. Sundial
b. Hourglass 

a. People in earlier days measured time using a sundial, which is a device that uses the position of the sun to indicate the time of day. The sundial consists of a flat plate with a raised edge or gnomon that casts a shadow on the plate. The position of the shadow indicates the time of day.

b. People in earlier days also used an hourglass to measure time. An hourglass is a device that consists of two glass bulbs connected by a narrow neck. Sand is placed in the top bulb, and as it falls through the neck into the bottom bulb, it measures a specific amount of time.

Q.3. Describe an activity to demonstrate the constancy of the time period of a pendulum. 

To demonstrate the constancy of the time period of a pendulum, one can set up a simple pendulum using a weight suspended from a string or rod. The pendulum should be set in motion and timed for several cycles. By measuring the time it takes for each complete cycle, it can be observed that the time period remains constant as long as the length of the pendulum remains the same.

Q.4. What is a distance-time graph? How can we find the speed of an object from its distance-time graph? 

A distance-time graph is a graphical representation of the distance covered by an object over a period of time. The horizontal axis represents time while the vertical axis represents distance. To find the speed of an object from its distance-time graph, one can calculate the slope of the graph. The slope represents the rate of change of distance with respect to time, which is the speed of the object.

Q.5. Distinguish between uniform and non-uniform motion. Also, give examples of each. 

Uniform motion is when an object covers equal distances in equal intervals of time, whereas non-uniform motion is when an object covers unequal distances in equal intervals of time. An example of uniform motion is a car traveling at a constant speed on a straight road. An example of non-uniform motion is a car accelerating or decelerating on a curved road.

Numerical Questions 

a. 40 minutes

b. 480 minutes

Q.2. a. How many hours are there in 3 days?
b. How many days are there in one decade? (Take 3654 days in each year.) 

a. 72 hours

b. 3654 x 10 = 36,540 days

Q.3. Calculate the number of minutes in a day. 

1440 minutes

Q.4. An object moves 360 km in 2 hours. Calculate its speed in km/h and m/s. 

Speed = Distance/Time

Speed = 360 km/2 hours = 180 km/h

Speed = 180 km/h = 50 m/s

Q.5. A car covers 240 km in 3 hours and a motorcycle covers 360 km in 4 hours. Which vehicle  is travelling faster? 

Car's speed = 240 km/3 hours = 80 km/h

Motorcycle's speed = 360 km/4 hours = 90 km/h

Motorcycle is travelling faster.

Q.6. Plane 'A' travels at 900 km/h and plane 'B' travels at 250 m/s. Which plane travels faster?

Plane A's speed = 900 km/h

Plane B's speed = 250 m/s = 0.25 km/s

Plane A travels faster.

Q.7. In a cricket match, on an average, it takes 5 minutes to bowl one over and 1 minute to  cross over after each over. How many overs (including the time taken for cross-over) can be finished in 1 hour? 

In 1 hour, there are 60 minutes.

Time taken for one over = 5 minutes + 1 minute (cross-over time) = 6 minutes

Number of overs in 1 hour = 60/6 = 10 overs

Q.8. Sonu goes for basketball coaching three times a week, and swimming classes two times  a week. Each basketball class is for 1 hour and 45 minutes, and each swimming class is for an hour. How much time does she spend in a week in these two classes? 

Total time for basketball coaching = 1 hour 45 minutes x 3 = 5 hours 15 minutes

Total time for swimming classes = 1 hour x 2 = 2 hours

Total time spent in these two classes = 5 hours 15 minutes + 2 hours = 7 hours 15 minutes

Q.9. If you travel by road, it takes 46 hours to travel from New Delhi to Kanyakumari. How  many days and hours would this be? 

46 hours = 2 days 22 hours

Q.10. Kushal loves to visit his grandparents every year to spend his summer holidays with  them. They live in a remote village. He takes a train, then a bus and then, walks the rest of the journey. The train travels at 60 km/h for 5 hours, the bus travels at 40 km/h for 3 hours and he walks at a speed of 5 km/h for 1 hour. What is the total distance he travels from the railway station to his grandparents' house? 

Total distance travelled = distance travelled by train + distance travelled by bus + distance travelled by walking

Distance travelled by train = 60 km/h x 5 hours = 300 km

Distance travelled by bus = 40 km/h x 3 hours = 120 km

Distance travelled by walking = 5 km/h x 1 hour = 5 km

Total distance travelled = 300 km + 120 km + 5 km = 425 km