question and answer for Time and motion of class 7
Answers
Question 1.
Give the basic unit of speed.
Answer:
Metre/second is the basic unit of speed.
Question 2.
Mention which is the most common thing in almost all the clocks.
Answer:
The most common thing in almost all the clocks is that all of them shows periodic motion.
Question 3.
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? [NCERT Exemplar; HOTS]
Answer:
They do not have equal speed because they cover unequal distance in equal intervals of time. One of them has higher speed whom has to cover larger distance with respect to other.
Question 4.
If Boojho covers a certain distance in one hour and Paheli covers the same distance in two hours, who travels with a higher speed? [NCERT Exemplar; HOTS]
Answer:
Boojho travels with a higher speed as he has covered same distance in lesser time with respect to Paheli.
Question 5.
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 non-uniform as it does not cover equal distance in equal intervals of time.
Question 6.
State the characteristic of distance-time graph for the motion of an object moving with a constant speed.
Answer:
The distance-time graph for the motion of an object moving with a constant speed is a straight line inclined on x-axis at some angles.
Question 7.
Name the axis that represents dependent variable.
Answer:
y-axis represents the dependent variable.
Question 8.
Briefly explain how will decide which object is moving fast and which one is moving slow.
Answer:
If an object covers more distance in equal intervals of time with respect to other, then we can say that object is moving faster with respect to the other object.
Question 9.
If you did not have a clock, how would you decide what time of the day is? [HOTS]
Answer:
We can decide time of the day without clock by seeing shadow formed by the sun, e.g. at noon, shadow formed by the sun is shorter than at evening.
Question 10.
State how do we measure time interval of a month.
Answer:
Time interval of a month is measured by one new moon to the next.
Question 11.
Determine the number of seconds there in a day.
Answer:
In a day, we have 24 h
We know that 1 h = 3600 s
So, 24 h = 3600 × 24 = 86400s
Question 12.
Estimate that how many hours are there in a year.
Answer:
In a year, we have 365 days and 1 day = 24 h
So, for 365 days, we have 24 × 365 h = 8760 h
Question 13.
Explain how time was measured when pendulum clocks were not available.
Answer:
Before the discovery of pendulum clocks, sundials, water clocks and sand clocks were used.
Question 14.
A spaceship travels 36000 km in one hour.Express its speed in km/s.
Answer:

Question 15.
Out of the two given clocks, a pendulum clock or a quartz clock. Mention which of the clock between the given ones requires an electric cell for its working?
Answer:
A quartz clock requires an electric cell for its working.
Question 16.
Name the most ancient unit of time in which it was earlier measured.
Answer:
Solar day is the most ancient unit of time in which it was earlier measured.
Question 17.
State the condition under which the distance-time graph of an object is a horizontal line parallel to the axis of time.
Answer:
When the object is at rest, then the distance-time graph of an object is a horizontal line parallel to the axis of time.
Question 18.
State the factors on which the time period of a simple pendulum depend.
Answer:
The factors on which the time period of a simple pendulum depend are
Length of the pendulum
Acceleration due to gravity.
Question 19.
Name the different types of graphs.
Answer:
Different types of graphs are
Line graph
Pie chart
Bar graph
Question 20.
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 different supports, so in this way, we can prepare a pendulum by our own.
.
.
.
hope it helps :)