Unit Test Solutions: Measurement of Time and Motion | Science (Curiosity) Class 7 - New NCERT PDF Download

Time: 1 Hour
Maximum Marks: 30

Instructions:

Attempt all questions.

Question numbers 1 to 5 carry 1 mark each .
Question numbers 6 to 8 carry 2 marks each.
Question numbers 9 to 11 carry 3 marks each.
Question numbers 12 and 13 carry 5 marks each.

Q1. Which device uses the Sun’s shadow to tell time? (1 Mark)
a) Water Clock
b) Sundial
c) Hourglass
d) Pendulum Clock

Answer: b) Sundial
Sol: A sundial uses the Sun’s shadow to show the time of day as the Sun moves across the sky.

Q2. What is the SI unit of time? (1 Mark)
a) Minute
b) Hour
c) Second
d) Ghati

Answer: c) Second
Sol: The second, symbolized as “s,” is the SI unit of time used worldwide.

Q3. What is the time period of a pendulum? (1 Mark)
a) Time to swing once
b) Time to stop swinging
c) Time to set up the pendulum
d) Time to measure distance

Answer: a) Time to swing once
Sol: The time period is the time a pendulum takes to complete one full swing, from one side to the other and back.

Q4. Which instrument in a car shows how fast it is going? (1 Mark)
a) Odometer
b) Speedometer
c) Clock
d) Thermometer

Answer: b) Speedometer
Sol: A speedometer shows a vehicle’s speed in km/h, like how fast a car is moving

Q5. What type of motion is a train moving at constant speed on a straight track? (1 Mark)
a) Non-uniform linear motion
b) Uniform linear motion
c) Circular motion
d) Random motion

Answer: b) Uniform linear motion
Sol: Uniform linear motion is when an object, like a train, moves in a straight line at a constant speed.

Q6. What is an hourglass, and how does it measure time? (2 Mark)

Sol: An hourglass is a device with two glass bulbs connected by a narrow neck, filled with sand. The sand flows from the top bulb to the bottom, and the time it takes to empty the top bulb shows a fixed amount of time,  like an hour.

Q7. What is a speedometer, and why is it useful for drivers? (2 Mark)

Sol: A speedometer is an instrument in vehicles to show the speed. It’s useful because it helps drivers know how fast they’re going, so they can stay within speed limits and drive safely.

Q8. What is non-uniform linear motion? Give one example. (2 Mark)

Sol: Non-uniform linear motion is when an object moves in a straight line but its speed changes, covering unequal distances in equal times. 
Example: A car slowing down at a traffic light.

Q9. What is the difference between an odometer and a speedometer? Give an example of how each is used. (3 Mark)

Sol: 
An odometer measures the total distance a vehicle travels in kilometres, while a speedometer shows how fast the vehicle is moving in km/h. For example, if you drive to a park, the odometer might show you’ve gone 20 km, helping you know when to service the car. 
The speedometer might show 40 km/h, helping you drive safely within the speed limit.

Q10. Calculate the speed of a car that travels 150 meters in 10 seconds. Express your answer in km/h. (3 Mark)

Sol: 
Speed = Distance / Time

Given:
Distance = 150 meters
Time = 10 seconds
Convert meters to kilometers and seconds to hours:
150 meters = 150/1000 =  0.15 km
10 seconds = 10/3600 hours = 1/360 hours
Now calculate speed:
Speed = 0.15 km / (1/360 hour) = 0.15 x 360 = 54 km/h

Q11.  Differentiate between circular motion and periodic motion. (3 Mark)

Sol: 
Circular Motion
Motion of an object in a circular path is called circular motion eg. Motion of the hands of a clock. 

Periodic Motion
When an object repeats its motion after some time. This type of motion is called periodic motion. e.g, Motion of a pendulum, motion of a child on a swing, motion of the strings of a guitar.

Q12.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:

Sol: 

Distance covered by the car with a speed of 40 km/h in 15 minutes = Speed x Time 

= (40 Km/h /60 minutes) x 15 minute 

= 10 Km 

Distance covered by the car with a speed of 40 km/h in 15 minutes = Speed  x Time 

= (60 Km/h /60 minutes) x 15 minute 

= 15 Km

Total distance covered by the car =(10 + 15 )km = 25 Km

Q13. A simple pendulum takes 15 seconds to complete 5 oscillations. What is the time period of pendulum?

Sol: 

The time taken by pendulum to complete 1 oscillation is called time period

The time taken by pendulum to complete 5 oscillation = 15sec

The time taken by pendulum to complete 1 oscillation = 15/5= 3 sec

So time period = 3 sec