KSEEB Solutions for Class 7 Science Chapter 13 Motion and Time

Students can Download Science Chapter 13 Motion and Time Questions and Answers, Notes Pdf, KSEEB Solutions for Class 7 Science helps you to revise the complete Karnataka State Board Syllabus and to clear all their doubts, score well in final exams.

Karnataka State Syllabus Class 7 Science Chapter 13 Motion and Time

Class 7 Science Motion and Time Textbook Exercise Questions and Answers

Question 1.
Classify the following as motion along a straight line, circular or oscillatory motion:

  1. The motion of your hands while running,
  2. The motion of a horse pulling a cart on a straight road,
  3. The motion of a child in a merry – go – round.
  4. The motion of a child on a see-saw.
  5. The motion of the hammer of an electric bell.
  6. The motion of a train on a straight bridge.

Answer:

  1. Oscillatory motion
  2. Straight-line motion
  3. Circular motion
  4. Oscillatory motion
  5. Oscillatory motion
  6. Straight-line motion.

KSEEB Solutions for Class 7 Science Chapter 13 Motion and Time

Question 2.
Which of the following are not correct?

  1. The basic unit of time is second.
  2. Every object moves at a constant speed.
  3. Distances between two cities are measured in kilometers.
  4. The time period of a given pendulum is constant.
  5. The speed of a train is expressed in m/h.

Answer:

  1. Correct
  2. Not correct
  3. Correct
  4. Not correct
  5. Not correct

Question 3.
A simple pendulum takes 32S to complete 20 oscillations. What is the time period of the pendulum?
Answer:
Time is taken = 32 seconds.
Number of oscillations = 20
Time period = ?
\(\text { Time period. }=\frac{\text { Total time taken }}{\text { Number of oscillations }}\)
\(=\frac{32}{20}=\frac{16}{10}=1.6\) Seconds
∴ The time period of the pendulum is 1.6 seconds.

KSEEB Solutions for Class 7 Science Chapter 13 Motion and Time

Question 4.
The distance between the two stations is 240 km. A train takes 4 hours to cover this distance. Calculate the speed of the train.
Answer:
Distance between two stations = 240 km
Time taken = 4 hr
∴ \(\text { Speed }=\frac{\text { Total distance }}{\text { Time taken }}=\frac{240}{4}\) = 60 km/hr
∴ The speed of the train is 60 km per hour.

Question 5.
The odometer of a car reads 57321,0 km when the clock shows the time 08 : 30 AM. What is the distance moved by 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 = 57321.0 km
Final reading = 57336.0 km
Total distance covered by the car = 57336 – 57321 = 15 km
Initial time = 08.30 AM
Final time =08.50 AM
Time taken = 20 min
\(Speed =\frac{\text { Total distance covered }}{\text { Time taken }}\)
\(=\frac{15}{20}=\frac{3}{4}\) km per minute = 0.75 x 60 = 45 km/hr
∴ The speed of the car is 45 km per hour.

KSEEB Solutions for Class 7 Science Chapter 13 Motion and Time

Question 6.
Salma takes 15 minutes from her house to reach her school on a bicycle. If the bicycle has a speed 2m/s, calculate the distance between her house and the school.
Answer:
Time taken = 15 min = 15 x 60 = 900sec
Speed of the bicycle = 2 m / sec
Distance = Speed x time taken
= 2 x 900
= 1800m
= 1.8 km

∴ The distance between Salma’s house and the school is 1.8 km.

Question 7.
Show the shape of the distance-time graph for the motion in the following cases:
(a) A car moving at a constant speed.
(b) A car parked on a side road.
Answer:
(a) A car moving with a constant speed covers equal distance in equal intervals of time.
KSEEB Solutions for Class 7 Science Chapter 13 Motion and Time 1

KSEEB Solutions for Class 7 Science Chapter 13 Motion and Time
(b) A car parked on a side road does not change in distance with an increase in time.
KSEEB Solutions for Class 7 Science Chapter 13 Motion and Time 2

Question 8.
Which of the following relations is correct?
(a) Speed = Distance x Time
(b) Speed = \(\frac{\text { Distance }}{\text { Time }}\)
(c) Speed = \(\frac{\text { Distance }}{\text { Time }}\)
(d) Speed = \(\frac{1}{\text { Distance } \times \text { Time }}\)
Answer:
(b) Speed = \(\frac{\text { Distance }}{\text { Time }}\)

Question 9.
The basic unit of speed is
(a) km/m in
(b) ni/min
(c) km/h
(d) m/s
Answer:
(d) m/s

KSEEB Solutions for Class 7 Science Chapter 13 Motion and Time

Question 10.
A car moves with a speed of 40 km/ h for 15 minutes and then with a speed of 60 km/h for the next 15 minutes. The total distance covered by the car is:
(a) 100 km
(b) 25 km
(c) 15 km
(d) 10 km
Answer:
(b) 25 km

Question 11.
Suppose the two photographs, shown below had been taken at an interval of 10 seconds. If a distance of 100 metres is shown by 1 cm in these photographs, calculate the speed of the fastest car.
KSEEB Solutions for Class 7 Science Chapter 13 Motion and Time 3

KSEEB Solutions for Class 7 Science Chapter 13 Motion and Time
Answer:
The distance covered by the car from one strip to another, which is measured by scale is 1.4 cm.
Given, 1 cm is equivalent to 100 m
∴ 1.4 cm is equivalent to = 1.4 x 100 = 140 m
∴ Distance travelled by the car = 140 m
Time interval between the two photographs = 10 s
∴ Speed = \(\frac{\text { Distance covered }}{\text { Time taken }}=\frac{140}{10}\) = 14 m/s
Thus, the speed of the fastest car is 14 m/s.

Question 12.
The figure shows the distance-time graph for the motion of two vehicles A and B. Which one of them is moving faster?
KSEEB Solutions for Class 7 Science Chapter 13 Motion and Time 4
Distance – time graph for the motion of two cars.
Answer:
Speed = \(\frac{\text { Distance covered }}{\text { Time taken }}\)
This relation shows that the speed of a vehicle is greater if it covers maximum distance at a given interval of time. The distance covered is compared by drawing a line perpendicular to the time axis.

KSEEB Solutions for Class 7 Science Chapter 13 Motion and Time
KSEEB Solutions for Class 7 Science Chapter 13 Motion and Time 5
At a given time t, the distance covered by vehicle A is more than vehicle B.
Hence, vehicle A is moving faster than vehicles.

Question 13.
Which of the following distance-time graphs shows a truck moving with a speed which is not constant?
KSEEB Solutions for Class 7 Science Chapter 13 Motion and Time 6
Answer:
(c) The graph shows that a truck is moving with a speed which is not constant.

KSEEB Solutions for Class 7 Science Chapter 13 Motion and Time

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