Q 1 – What is the use of speedometer?
Ans. Speedometer is a device which is used in vehicles to measure the distance covered by the vehicle.
Q 2 – What is uniform motion?
Ans. Uniform motion is that type of motion in which body travels equal distances in equal intervals of time.
Q 3 – What is speed?
Ans. The speed of an object is defined as the distance travelled by the object in unit time.
Q 4 – Which unit of speed will you use to express the speed of an aeroplane?
Ans. km/s
Q 5 – Which kind of motion is described by a freely falling body?
Ans. Linear motion.
Q 6 – What is the name of the device which measures the speed of a moving vehicle?
Ans. Odometer
Q 7 – If A covers a certain distance in 30 minutes and B covers the same distance in 45 minutes, then who is travelling in higher speed?
Ans. A is taking less time to cover the same distance, so it is travelling in higher speed.
Q 8 – What is the relation between distance and speed?
Ans. Distance = Speed × Time
Q 9 – On what the time period of a simple pendulum depends?
Ans. The time period of a simple pendulum depends upon its length.
Q 10 – What is motion? Describe briefly.
Ans., An object that is moving with respect to time and another body is said to be in motion. Motion is measured as the distance covered by an object in a specific interval of time.
Q 11 – Differentiate between slow and fast objects.
Ans. An object which takes longer time to cover a certain distance is called slow whereas another object which takes a shorter time to cover the same distance is called fast.
Q 12 – Anshika takes 15 minutes from her house to reach her school on bicycle the distance between her house and the school.
Ans. Time taken = 15 min.
Speed = 2 m/s
Distance = Speed × time
= 15 × 60 × 2 = 1800 m
Thus, the distance between Anshika’s house and her school is 1800 m.
Q 13 – What are the factors on which time period of a pendulum depends?
Ans. Following are the factors on which time period of a pendulum depends
- Length of the string of the pendulum.
- Acceleration due to gravity.
Q 14 – State one factor which is common in all the clocks.
Ans. All the clocks show periodic motion.
Q 15 – The average age of students of class VII B is 12 years 4 months. Express the age in seconds.
Ans. 12 years 4 months = 12 × 365 + 4 × 30 = 4500 days
4500 days = 4500 × 24 × 60 × 60 = 388800000 s
Q 16 – Sitting in a classroom each student appears stationary to each other, whereas actually they are in motion.
Ans. This is because of the earth in which we live is always in a state of motion around the sun and also along its axis.
Q 17 – Write some types of motion.
Ans. Rectilinear motion, oscillatory motion, rotatory motion, random motion, etc.
Q 18 – What is rectilinear motion.
Ans. When the motion of a body is along a straight line, it is known as rectilinear motion.
Q 19 – What is rotatory or circular motion.
Ans. When a body moves about a fixed axis without changing its position, the body is said to have a rotatory motion.
Q 20 – Who among, Ritesh and Saket, is correct? Explain.
Ans. Ritesh and Saket, both are correct because wheels of the bicycle is showing both types of motion, i. e., rectilinear motion along the road as well as rotational or circular motion along a fixed axis.
Q 21 – What value of Ritesh and Saket is shown here?
Ans. Ritesh and Saket both are intelligent and mature enough to not quarrel and inquisitive
Q 22 – State the difference between uniform motion and non-uniform motion.
Ans. ‘
| 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. |
| (iii) The distance-time graph for non-uniform motion is a curved line. | (iii) The distance-time graph for uniform motion is a straight line. |
Q 23 – Give the basic unit of speed.
Ans. Metre/second is the basic unit of speed.
Q 24 – Mention which is the most common thing in almost all the clocks.
Ans. The most common thing in almost all the clocks is that all of them shows periodic motion.
Q 25 – 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?
Ans. 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.
Q 26 – If Boojho covers a certain distance in one hour and Paheli covers the same distance in two hours, who travels with a higher speed?
Ans. Boojho travels with a higher speed as he has covered same distance in lesser time with respect to Paheli.
Q 27 – State the characteristic of distance-time graph for the motion of an object moving with a constant speed.
Ans. 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.
Q 28 – Name the axis that represents dependent variable.
Ans. y-axis represents the dependent variable.
Q 29 – Briefly explain how will decide which object is moving fast and which one is moving slow.
Ans. 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.
Q 30 – If you did not have a clock, how would you decide what time of the day is?
Ans. 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.
Q 31 – State how do we measure time interval of a month.
Ans. Time interval of a month is measured by one new moon to the next.
Q 32 – Determine the number of seconds there in a day.
Ans. In a day, we have 24 h
We know that 1 h = 3600 s
So, 24 h = 3600 × 24 = 86400s
Q 33 – Estimate that how many hours are there in a year.
Ans. In a year, we have 365 days and 1 day = 24 h
So, for 365 days, we have 24 × 365 h = 8760 h
Q 34 – Explain how time was measured when pendulum clocks were not available.
Ans. Before the discovery of pendulum clocks, sundials, water clocks and sand clocks were used.
Q 35 – 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?
Ans. A quartz clock requires an electric cell for its working.
Q 36 – Name the most ancient unit of time in which it was earlier measured.
Ans. Solar day is the most ancient unit of time in which it was earlier measured.
Q 37 – State the condition under which the distance-time graph of an object is a horizontal line parallel to the axis of time.
Ans. When the object is at rest, then the distance-time graph of an object is a horizontal line parallel to the axis of time.
Q 38 – State the way through which we can prepare a pendulum by our own.
Ans. 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.
Q 39 – Differentiate between a uniform and non-uniform motion.
Ans. When a body travels equal distance in an equal interval of time, then the body is said to be in a uniform motion.
When a body travels unequal distance in an equal interval of time, then the body is said to be in non-uniform motion.
Q 40 – What is the relation between distance and speed?
(a) Distance = Speed × Time
(b) Distance = Speed/Time
(c) Distance = Time/Speed
(d) None of the above
Ans. (a) Distance = Speed × Time
Q 41 – The distance-time graph for the motion of an object moving with a constant speed is
(a) a curved line leaving towards x-axis
(b) a curved line inclined towards y-axis
(c) a straight line inclined at some angles towards x-axis
(d) None of the above
Ans. (c) a straight line inclined at some angles towards x-axis
Q 42 – The distance-time graph for a vehicle standing on a road side will be
(a) straight line inclined by some angle to x-axis
(b) straight line parallel to x-axis
(c) straight line parallel to y-axis
(d) None of the above
Ans. (b) straight line parallel to x-axis
Q 43 – Which of the following cannot be used for the measurement of time?
(a) A leaking tap
(b) Simple pendulum
(c) Shadow of an object during the day
(d) Blinking of eyes
Ans. (d) Blinking of eyes