Get the simplified Class 7 Science Extra Questions and Class 7th Curiosity Chapter 8 Measurement of Time and Motion Important Extra Question Answer with complete explanation.
Class 7 Science Chapter 7 Measurement of Time and Motion Extra Questions
Class 7 Science Chapter 8 Extra Questions on Measurement of Time and Motion
Measurement of Time and Motion Class 7 Very Short Question Answer
Question 1.
If Boojho covers a certain distance in one hour and Paheli covers the same distance in two hours, who travels with a higher speed?
Answer:
Boojho travels with a higher speed as he has covered same distance in lesser time with respect to Paheli.
Question 2.
Paheli and Boojho have to cover different distances to reach their school but they take the same time to reach the school. What can you say about their speed?
Answer:
They do not have equal speed because they cover ’ unequal distances in equal intervals of time.
One of them has higher speed whom has to cover larger distances with respect to other.
Question 3.
Give the basic unit of speed.
Answer:
Metre/second is the basic unit of speed.
Question 4.
A spaceship travels 36000 km in one hour. its speed in km/s.
Answer:
As, speed = \(\frac{distance}{time }\)
= \(\frac{36000}{1 \times 3600}\) [ ∴ 1h = 3600 s]
= 10 km/s
Question 5.
Mention which is the most common thing in almost ail the clocks.
Answer:
The most common thing in almost all the clocks is that all of them show periodic motion.
Question 6.
Out of the two given clocks, a pendulum clock or a quartz clock, mention which of the clocks require an electric cell for its working?
Answer:
A quartz clock requires an electric cell for its working.
Question 7.
State the factors on which the time period of a simple pendulum depends.
Answer:
The factors on which the time period of a simple pendulum depends are
(i) Length of the pendulum
(ii) Acceleration due to gravity
Question 8.
State the way through which we can prepare a pendulum by our own.
Answer:
By suspending a metal ball with the help of a cotton thread and the other end of the thread can be tied to some fixed support. In this way, we can prepare a pendulum by our own.
Question 9.
A simple pendulum is oscillating between two points A and B as shown in figure. Is the motion of the bob uniform or non-uniform?
Answer:
The motion of bob is uniform as it covers equal distance in equal intervals of time.
Question 10.
State the difference between uniform motion and non-uniform motion.
| Non-uniform motion | Uniform motion |
| (i) If the speed of an object moving along a straight line keeps changing, then this type of motion is called non-uniform motion. | (i) If the speed of an object moving along a straight line remains constant, then this type of motion is said to be uniform motion. |
| (ii) In this case, average speed is generally different from the actual speed. | (ii) In this case, the average speed is same as the actual speed. |
Measurement of Time and Motion Class 7 Short Question Answer
Question 1.
Why do we need to measure time?
Answer:
We need to measure time for the different reasons
- Doctors need to measure the number of times the heartbeat occurs in one minute for a patient.
- Farmers need to measure the time between sowing and harvesting of crops.
- A sportsman needs to measure the time he might take to complete an event.
- A traveller needs to measure the time of his journey.
- Students need to measure the time to complete an event.
Question 2.
How did ancestors measure a day, month and year?
Answer:
Our ancestors noticed that many events in nature repeat themselves after regular definite intervals of time. By looking at the regular events they were able to predict the day, month and year. The time between one sunrise and the next was called a day. A month was measured from one new moon to the next. A year was measured as the time taken by the earth to complete one revolution.
Question 3.
One day, a five years old boy Chintoo was playing with his toys in his room. After few minutes, he saw a wristwatch on his study table, so after seeing it, he got crazy and so much eager to play with that watch. Then, for 2 to 3 min, he was trying to analyse it that whether it’s a toy or something else, then suddenly, he was just about to throw it but at the same time his mother entered into the room and took the watch back immediately from his hand.
(i) State the benefits of a wristwatch.
(ii) Briefly mention the values showed by Chintoo’s mother here.
Answer:
(i) The wristwatch can be handled very easily to check the time in comparison to the wall clock.
(ii) The values showed by Chintoo’s mother here is the concern towards her five years old child and also the concern towards that wristwatch while considering the importance of money.
Question 4.
The average age of children of class VII is 12 years and 3 months. Express their age in second.
Answer:
Given, the average age of children 12 years and 3 months
1 year = 365 days = 365 × 24 h [1 day = 24 h]
= 365 × 24 × 3600 s [1 h = 3600 s]
12 years = 31536000 s × 12 = 378432000 s
3 months = 30 × 3 days = 30 × 3 × 24 h
= 30 × 3 × 24 × 3600s
= 7776000 s
So, total age in second = 378432000 + 7776000
= 386208000s
Question 5.
Last Sunday, Priyanka decided to go outside with her family for dinner in some particular restaurant. Then, she thought to go through her own car. So, while moving she increased the speed of the car from 36 km/h to 54 km/h.
All of sudden, a rickshaw came in front of her car but by applying brakes at the right time, both of them were saved from meeting with an accident.
(i) Calculate the increase in the speed of the car in the terms of m/s.
(ii) Mention a positive action performed by Priyanka here.
Answer:
(i) Initial speed = 36 km/h = \(\frac{5}{18}\) x 36 = 10 m/s
Final speed = 54 km/h = \(\frac{5}{18}\) x 54
= 15 m/s
∴ Increase in speed = Final speed – Initial speed
= (15 – 10) m/s
= 5 m/s
(ii) Priyanka applied the brakes at the right time while driving the car and prevented her family and the person on rickshaw from meeting with an accident.
Question 6.
Three students start running from the starting point at the same time. The picture shows the position of the students on the path after a minute.
Which student ran the fastest? Explain your answer.
Answer:
Student 3 ran the fastest as compared to the other students because he covered the maximum distance in the same time.
Question 7.
Rockets, launching satellites into earth’s orbit, often attain speeds up to 8 km/s. On the other hand, a tortoise can move only with a speed of about 8 cm/s. Can you calculate how fast is the rocket compared with the tortoise?
Answer:
Speed of rocket = 8 km/s = 8 x 1000 m/s = 8000 m/s
Speed of tortoise = 8 cm/s = 8/100 m/s
Hence, \(\frac{8000}{(Speed of rocket / Speed of tortoise)}\) = \(\frac{8000}{(8 / 100)}\)
= 8000 x \(\frac{100}{8}\) = 100000
Therefore, the rocket is 100000 times or 105 times faster than the tortoise.
Measurement of Time and Motion Class 7 Long Question Answer
Question 1.
What is a simple pendulum? Explain how it works and how it can be used to measure time.
Answer:
A simple pendulum is a device made of a small heavy object, called a bob, suspended from a fixed point by a string or thread that allows it to swing freely. When the bob is pulled to one side and released, it swings back and forth in a regular manner. This back-and-forth motion is called an oscillation.
- One oscillation is when the pendulum moves from one extreme position to the other and returns to its starting point.
- The time period of a pendulum is the time which takes to complete one oscillation. It is measured using a stopwatch or a clock.
- The time period depends mainly on the length of the string. It does not depend on the mass of the bob or the amplitude (as along as the swing is small).
- Since, the motion of a pendulum is regular and periodic, it can be used to measure time accurately.
Question 2.
Suppose the two photographs, shown in Fig. (a) and Fig. (b), had been taken at an interval of 10 s. If the distance of 100 m is shown by 1 cm in these photographs, calculate the speed of the fastest car.
Answer:
The distance covered by the blue car (as evident from the photograph) from one horizontal white strip to another, which is measured by scale is 1.2 cm.
It is given that 1 cm is equivalent to 100 m.
Therefore, 1.2 cm is equivalent to 120 m.
Distance travelled by the car = 120 m
Time taken to cover this distance = Time interval
between the two photographs = 10 s
Speed = \(\frac{Distance covered}{Time taken}\)
\(\frac{120}{10}\) = 12 m/s
Question 3.
A car moves with a speed of 40 km/h for 15 min and then with a speed of 60 km/h for the next 15 min.
Find the total distance covered.
Answer:
When the speed of the car is 40 km/h
Time taken = 15 min = \( \frac{15}{60}\) = 025 h 60
Speed = \(\frac{Distance covered}{Time taken}\)
Distance covered, d1 = Speed x Time taken
= 40 × 0.25 = 10 km
When the speed of the car is 60 km/h
Speed = \(\frac{Distance covered}{Time taken}\)
Distance covered, d2 = Speed x Time taken
= 60 × 0.25 = 15km
Total distance covered by the car = d1 + d2
= 10 + 15 = 25 km
Question 4.
Distance between Bholu’s and Golu’s house is 9 km. Bholu has to attend Golu’s birthday party at 7 o’ clock. He started his journey from his home at 6 o’ clock on his bicycle and covered a distance of 6 km in 40 min. At that point, he met Chintu and he spoke to him for 5 min and reached Golu’s birthday party at 7 o’ clock. With what speed, did he cover the second part of the journey? Calculate his average speed for the entire journey?
Answer:
According to question, Bholu covers the remaining 3 km distance in 15 min.
So, speed of Bholu = \(\frac{3}{15}\) × 60
= 12 Km/h
Now, average speed of Bholu during the entrie journey is
= \(\frac{total distance travelled}{total time taken}\)
= \(\frac{9}{1}\) = 9 km/h
Question 5.
The odometer of a car reads 57321.0 km when the clock shows the time 08:30 a.m., What is the distance moved by the car, if at 08:50 am, the odometer reading has changed to 57336.0 km? Calculate the speed of the car in km/min during this time. Express the speed in km/h also.
Answer:
Initial reading of the odometer = 573210
Final reading of the odometer = 57336.0
Distance covered by the car = Final reading of the odometer – Initial reading of the odometer
= 57336.0 – 5732L0 = 15 km
Starting time of car is 8:30 a.m.
and it stops at 8:50 a.m.
Flence, time taken by car = 20 min
Speed = \(\frac{Distance}{Time}\)
= \(\frac{15}{20}\)
= 0. 75 Km/min
Now, 20 min = \(\frac{1}{60}\) x 20 hours
= \(\frac{1}{3}\)h
Speed = \(\frac{\text { Distance covered }}{\text { Time taken }}\) = \(\frac{15}{1 / 3}\)
= 45 km/h
Measurement of Time and Motion Class 7 Case Based Questions
Question 1.
The timetable of a train is shown below
| Station | Arrival | Departure |
| New Delhi | 06.45 a.m. | |
| Meerut | 08.03 a.m. | 08.05 a.m. |
| Muzaffarnagar | 08.45 a.m | 08.47 a.m. |
| Saharanpur | 09.50 a.m. | 09.55 a.m. |
| Roorkee | 10.30 a.m |
(i) What is the total travel time of the train?
(a) 3 h 30 min
(b) 3 h 45 min
(c) 4 h 15 min
(d) 4 h 45 min
(ii) The distance between Meerut and Muzaffarnagar is about 60 km. Calculate the average speed of the train (in km/h), while travelling between the two stations.
Answer:
1. (i) (b) 3 h 45 min
(ii) Total distance = 60 km
Total time = 40 min or 2/3h
Speed = \(\frac{\text { Total distance }}{\text { Total time }}\) = \(\frac{60}{2}\) × 3 = 90 Km/h
Measurement of Time and Motion Class 7 Skill Based Questions
Question 1.
A simple pendulum is observed during a lab activity. Students record the time it takes for 20 oscillations.
Pendulum 1: 30 seconds
Pendulum 2 : 40 seconds
Pendulum 3 : 50 seconds
(i) Which pendulum has the longest time period?
(a) Pendulum 1
(b) Pendulum 2
(c) Pendulum 3
(d) All of these
Answer:
Time period T = \(\frac{\text { Total time }}{\text { Number of oscillations }}\)
So,
Pendulum 1 : T = \(\frac{20}{20}\) = l.5s
Pendulum 2 : T = \(\frac{40}{20}\) = 2.0s
Pendulum 3 : T = \(\frac{50}{20}\) = 2.5s
Answer (c) Pendulum 3
(ii) If the length of pendulum 3 is increased further, what will happen to its time period?
(a) It will decrease
(b) It will remain unchanged
(c) It will increase
(d) It will become zero
Answer:
(c) It will increase
Question 2.
Bholu and Golu are playing in a ground. They start running from the same point A in the ground and reach point B at the same time by following the paths marked 1 and 2, respectively as shown in the figure. Which of the following is true for the given situation?
As compared to Golu, Bholu covers a
(a) longer distance with a lower speed
(b) longer distance with a higher speed
(c) shorter distance with a lower speed
(d) shorter distance with a higher speed
Answer:
(b) longer distance with a higher speed
Question 3.
Rahul had an official meeting in Delhi, so he booked a taxi to travel from Lucknow to Delhi. The taxi driver asked Rahul to come to the nearest pick-up point at 6 a.m. When Rahul seated in the taxi, he noticed that the odometer of the taxi read 13000 km. He reached Delhi in 6 h. At the end of the trip, he checked that the odometer read 13600 km.
(i) The odometer of the taxi measured its
(a) total time
(b) total speed
(c) total distance
(d) Both (a) and (b)
Answer:
(c) total distance
(ii) An automobile moving on a busy road is an example of
(a) uniform motion
(b) non-uniform motion
(c) circular motion
(d) periodic motion
Answer:
On a busy road, the automobile keeps changing its speed and direction due to traffic, signals, turns, etc. Hence, it is non-uniform motion.
Measurement of Time and Motion Extra Questions for Practice
Question 1.
A simple pendulum takes 20 s to complete 10 oscillations. Calculate the time period of the pendulum.
Question 2.
A car travels 150 km in 3 h. What is its average speed? Also, explain whether this motion is uniform or non-uniform, if it changes speed during the journey.
Question 3.
Name the instrument which is used
(a) to record the distance covered by a vehicle.
(b) to indicate the speed of a running vehicle.
Question 4.
A car travelling at a speed of 60 km/h takes 20 min to reach its destination. What distance has the car covered?
Question 5.
Write the use of odometer in the vehicle.
Question 6.
(i) Name the watch that have an electric circuit with one or more cells.
(ii) Name the ancient time measuring device.
Question 7.
What are the factors that affect the time period of a simple pendulum? Explain why increasing the mass of the bob does not change the time period.
Question 8.
What is speed? Derive the formula for average speed and explain how it is affected when the total distance remains constant but time changes. Give numerical examples. A pendulum has a time period of 2 s. How can it be used as a timekeeping device? What are the limitations of using a simple pendulum for measuring time in daily life?