These AP 7th Class Science Important Questions and 9th Lesson Motion and Time Class 7 Extra Questions will help students prepare well for the exams.
Class 7 Science Motion and Time Extra Questions
Motion and Time Class 7 Important Questions
Question 1.
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 the bob is non-uniform because the speed of the bob keeps changing as it does not cover equal distance in equal intervals of time.
Question 2.
If Shyam covers a certain distance in one hour and Ram covers the same distance in two hours, who travels in a higher speed?
Answer:
Ram travels with a higher speed, as he has covered the same distance in lesser time than Shyam.
Question 3.
What is a motion?
Answer:
Motion is defined as there is a change in the position of an object with the time.
Question 4.
Define Speed.
Answer:
The distance travelled by an object in a unit time (either in one hour, in one minute or in one second) is known as speed of the object.
\(\text { Speed }=\frac{\text { Distance travellèd }}{\text { Time taken }}\)
Question 5.
Define time period.
Answer:
The time taken by the pendulum to complete one oscillation is called its time period
Question 6.
What is an oscillatory motion?
Answer:
The to and fro motion of an object is called oscillatory motion.
Question 7.
Give any two examples of periodic motion.
Answer:
Examples of periodic motion are :
- Rotation of earth on its axis.
- Moon moves around the earth.
Question 8.
What is the unit of speed?
Answer:
The unit of speed is meter per second.
Question 9.
What do you mean by uniform motion?
Answer:
An object moving along a straight line keeps changing, its motion is said to be non uniform motion.
Question 10.
What do you mean by non – uniform motion?
Answer:
An object moving along a straight line with a constant speed; in the motion is said to be uniform motion.
Question 11.
What is bob?
Answer:
The metallic ball is called bob of the pendulum.
Question 12.
What devices do we use to measure intervals of time which are much shorter than a day?
Answer:
The most common time measuring devices used are docks or watches.
Question 13.
What are the various types of graphs?
Answer:
The various types of graphs are pie chart, bar graph, and line graph.
Question 14.
What is speedometre?
Answer:
Speedometer is an instrument used for measuring on a vehicles dashboard, which indicates the speed of the vehicle when it is done. It requires the speed directly in km/h.
Question 15.
What is odometer?
Answer:
Odometer is an instrument for measuring the distance travelled by the vehicle. It records the distance travelled by the vehicle in kilometre.
Question 16.
Where will you find speedometers and odometers.
Answer:
Speedometers and odometers will be seen on the dashboards of buses, cars, and other vehicles.
Question 17.
Name some devices which are used to measure time.
Answer:
Quartz clock, sundial and sand clock are devices used to measure time.
Motion and Time Extra Questions
Question 1.
Complete the data of the table given below with the help of the distance-time graph given in figure.
| Distance (m) | 0 | 4 | ? | 12 | ? | 20 |
| Time (s) | 0 | 2 | 4 | ? | 8 | 10 |
Answer:
| Distance (m) | 0 | 4 | 8 | 12 | 16 | 20 |
| Time (s) | 0 | 2 | 4 | 6 | 8 | 10 |
Question 2.
What do you understand by periodic motion? Give any examples.
Answer:
The motion which repeats itself after regular intervals of time, is called periodic motion. Periodic motion of a simple pendulum has been used to make clocks and watches.
Examples:
- The motion of the swing, to and fro motion of a simple pendulum.
- The rotation of the earth on its axis, and the revolution of the earth around the sun.
Question 3.
What are quartz clocks?
Answer:
The clocks or watches have an electric circuit with one or more cells are called quartz clocks. The time measured by quartz clocks is much more accurate than that by the clocks available earlier.
Question 4.
What do you mean by the statement; “car is moving with the speed of 70Km per hour”?
Answer:
Car is moving with the speed of 70 km per hour it means it will cover a distance of 70 km in one hour.
Question 5.
A spaceship travels 36000 km in one hour. Express its speed in km/s.
Answer:
Given, Distance travelled by spaceship = 36000 km
Time taken = 1 hour
We know, 1 hour =60 min= 60 × 60 = 3600 seconds
\(\text { Speed }=\frac{\text { Distance, } \text { travelled }}{\text { Time taken }}=\frac{36000}{3600}=10 \mathrm{~km} / \mathrm{s}\)
Question 6.
Plot a distance-time graph of the tip of the second hand of a clock by selecting 4 points on X-axis and Y-axis, respectively. The circumference of the circle traced by the second hand is 64 cm.
Answer:
Given the distance covered in 60 seconds = 64 cm
The distance covered in 15 seconds = 16 cm
Similarly, the distance covered in 30 seconds = 32 cm (30/60 x 64)
The distance covered in 45 seconds = 32 cm (45/60 x 64)
The circumference of circle traced by a second hand in 60 sec is 64 cm.
| Time (s) | X | 15 | 30 | 45 | 60 |
| Distance (m) | Y | 16 | 32 | 48 | 64 |
Here equal distance is covered in equal interval of time. So the graph will be a straight line.
Question 7.
A boy runs 20km in 2 hours. How long will he take to run 40 km at double the previous speed?
Answer:
A boy runs 20 km in 2 hours.
\(\text { Speed }=\frac{\text { Distance travelled }}{\text { Time taken }}=\frac{20}{2}=10 \mathrm{~km} / \mathrm{h}\)
He will take time to run 40 km at double the previous speed is (40/10)=4hours
Question 8.
Why do we need to measure time?
Answer:
We need to measure the time for the different reasons:
- Doctors need to measure the number of times the heartbeat 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 need to measure the time of his journey.
- Students need to measure the time to complete an event.
Question 9.
What are the difference between slow and fast motion?
Answer:
The differences between slow and fast objects.
| S.No. | Slow motion | Fast motion |
| 1) | An object which takes a long time to cover a certain distance is known as slow motion. | An object which takes shorter time to cover the certain distance is known as fast motion. |
| 2) | Example : Motion of tortoise and snail. | Example : Racing car and leopard. |
Question 10.
What are the factors on which the time period of a pendulum depends?
Answer:
The time period of a simple pendulum does not depend on the mass of the bob and nature of the material of the bob. It depends upon the length of the pendulum and acceleration due to gravity.
Question 11.
The average age of children of class VII is 12 years and 3 months. Express this age in
second.
Answer:
Given, the average age of children 12 years and 3 months
1 year = 365 days = 365 x 24 h [ 1 day = 24 h]
= 365 x 24 x 3600 s [1 h = 3600 s]
12 years = 31536000 s x 12 = 378432000 s
3 months = 30 x 3days = 30 x 3 x 24h
= 30 x 3 x 24 x 3600s
= 7776000s
So, total age in second = 378432000 + 7776000 = 386208000s.
Question 12.
Find the speed of a car that travels in 500 km in 5 hours.
Answer:
Given,Distance covered = 500 km
Time taken =5 hours
\(\text { Speed }=\frac{\text { Distance travelled }}{\text { Time taken }}=\frac{500}{2}=100 \mathrm{~km} / \mathrm{h}\)
Speed = 100 km/h
Question 13.
What are the points that should be considered while choosing the most suitable scale for drawing
Answer:
The following points should be considered while choosing the most suitable scale for drawing a graph:
- The difference between the highest and lowest values of each quantity.
- To utilise the maximum part of the graph paper.
- The intermediate values of each quantity, so that the scale chosen it is convenient to mark the values on it.
Question 14.
What does the path of an object look like when it is a non-uniform motion?
Answer:
In non-uniform motion, the path of an object can be a curved line, zigzag line or even a circle. It can have any shape. This is because in non-uniform motion speed is not constant. The direction of motion may change.
Question 15.
Convert 36km/h into m/s.
Answer:
To convert 36 km/h into m/s; Multiply by \(\frac{5}{18}\)
1km =1000m and 1 hour =3600s
\(\frac{1 \mathrm{~km}}{1 \text { hour }}=\frac{1000}{3600}=\frac{5}{18} \mathrm{~km} / \mathrm{h}=36 \times \frac{5}{18} \mathrm{~m} / \mathrm{s}\)
Extra Questions of Motion and Time Class 7
Question 1.
Write the differences between uniform motion and non-uniform motion.
Answer:
The difference between uniform motion and non-uniform motion are as follows:
| S.No. | Uniform motion | Non uniform motion |
| 1) | An object moving along a straight . line with a constant speed is said to be in uniform motion. | An object moving along a straight line with a constant speed, in the motion is said to be uniform motion. |
| 2) | It covers equal distances at an equal interval of time. | It covers unequal distances at equal interval of time. |
| 3) | The distance time graph is a straight line curved line. | The distance time graph shows a |
| 4) | Average speed is similar to the actual speed of the object. | Average speed is different frome actual speed of the object. |
| 5) | Rectilinear motion has zero acceleration. | Motion has non- zero acceleration. |
Question 2.
Prem goes to the football ground to play football.
The distance-time graph of his journey from his home to the ground is given as figure.
i) What does the graph between points B and C indicate about the motion of Boojho?
ii) Is the motion between 0 to 4 min uniform or non uniform?
iii) What is his speed between 8 and 12 minutes of his journey?
Answer:
i) Prem’s speed is zero hence he will be in rest because the graph between B and C is parallel to time-axis.
ii) The graph is not straight line, so it is a non-uniform motion.
\(\text { Speed }=\frac{\text { Distance travelled }}{\text { Time taken }}=\frac{225-150}{12-8}=\frac{75}{4}=18.75 \mathrm{~m} / \mathrm{min}\)
Question 3.
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 4.
What are the advantages of graphs ?
Answer:
The advantages of graphs are:
- It helps in the comparison of data in a better way.
- The interdependence of two variables can be established easily.
- The mean value of ratio of two variables can be accurately obtained without rigorous mathematical calculations.
- The probable value of variables can be calculated with the help of a graph within, or beyond the observed values from the mean value without any lengthy numerical computations.
- Another important advantage of the graph is that some of the salient features of the given experimental data can be seen visually, which cannot be easily concluded by simply looking the experimental data.
Question 5.
How will you make a line graph ?
Answer:
The following steps will be followed to make a graph:
- Draw two perpendicular lines to represent the two-axis and mark them as OX and OY.
- Show time along X -axis and distance along the Y -axis.
- Choose a scale to represent distance and another scale to represent the time on the graph.
- Mark values for the time and distance on the respective scales.
- Join all the points on the graph.
Question 6.
What information is provided by the distance-time graph?
Answer:
The information provided by the distance-time graph is as follows:
- It tells about the distance moved by the object only at some definite time intervals.
- We can find the distance moved by the object at any instant in time.
- We can calculate the speed of the object from the distance-time graph.
Case Based / Data – Based Questions
Hema was driving a car on the road, she said that the wheels of the car are moving along a straight line. But her friend, Ram who was riding a bicycle, said that the wheels of the car are moving circular. Then they decided rather than fighting themselves, it is better to ask their science teacher.
i) What is rotational motion?
Answer: The motion possessed by a body when it spins about a fixed axis, is called rotational motion.
ii) Name some types of motion.
Answer: The types of motion are circular motion, oscillatory motion, periodic motion, rectilinear motion etc.
iii) Among Hema and Ram who is correct? Explain.
Answer: Hema and Ram, both are correct because the wheels of the car is showing both types of motion i.e., rectilinear motion along the road as well as rotational or circular motion along fixed axis.
iv) What is rectilinear motion?
Answer: When the motion of a body along a straight line, it is known as rectilinear motion