Motion And Time(7th Grade > Physics ) Questions and answers for exam Preparation

7th Grade > Physics

MOTION AND TIME MCQs

Total Questions : 115 | Page 2 of 12 pages

Question 11. If you are resting inside a car that is moving, are you in rest or motion? Justify your answer. [3 MARKS]

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Correct answer: 1.5 Marks
Justification: 1.5 Marks
If you are sitting inside a car that is moving, then you are in a state of rest with respect to the car but in a state of motion with respect to the surroundings outside the car.
When a person is sitting inside a car, the person's position with respect to the car is not changing but hisposition with respect to surroundings outside the car is changing.

If You Are Resting Inside A Car That Is Moving, Are You In R...

Question 12. A car moves with a speed of 40 km/hr for 15 minutes and then with a speed of 60 km/hr for the next 15 minutes. What is the total distance covered by the car? Also, find the average speed of the car. [5 MARKS]

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Steps: 1 Marks
Distance: 2 Mark
Average Speed: 2 Mark
15 minutes

= \frac{15}{60} h r s = 0.25 h r s

Distance covered in first 15 minutes

= s p e e d \times t i m e

= 40 \times 0.25 = 10 k m

Speed of car changes to 60 km/hr and it travels for another 15 min.
Distance covered in next 15 minutes

= s p e e d \times t i m e

= 60 \times 0.25 = 15 k m

Total distance covered in 30 minutes = 10 + 15 = 25 km
Average speed

= \frac{T o t a l D i s t a n c e}{T o t a l t i m e}

= \frac{25}{0.5}

= 50 km/hr

Question 13. Rahul runs for 20 mins at the speed of 20 km/hr after which he gets tired. He still manages to run for 10 mins but at a lesser speed of 10 km/hr. How much distance did Rahul cover? [2 MARKS]

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Calculation: 1 Mark
Result: 1 Mark
Distance covered in first 20 mins or one-third of an hour = one-third of 20 km (Since speed is 20 km/hr).
Distance covered in last 10 mins or one-sixth of an hour = one-sixth of 10 km (Since speed is 10 km/hr).

T o t a l d i s t a n c e c o v e r e d = \frac{20}{3} + \frac{10}{6}

T o t a l d i s t a n c e c o v e r e d = \frac{50}{6} k m s

= 8.33 k m

Question 14. What is translatory motion? [1 MARK]

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Definition: 1 Mark
Translational motion is the motion of body where body moves in the linear path. It is the motion in which all points of a moving body move uniformly in the same line or direction.

Question 15. A girl decides to go for shopping. The mall is 5 km from her home. She covers the first 3 km at a speed of 30 km/hr. She is stuck in traffic for 6 minutes and covers rest of the distance at 40 km/hr. How much time did she take to reach the mall? Also, find her average speed. [5 MARKS]

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Total Time: 2 Marks
Average speed: 1 Mark
Formula: 1 Mark
Steps: 1 Mark
Time taken to cover first 3 km

= \frac{3}{30} = \frac{1}{10} h r

Time taken to cover last 2 km

= \frac{2}{40} = \frac{1}{20} h r

Time she was stuck in traffic = 6 min

= \frac{6}{60} = \frac{1}{10} h r

Total time taken

= \frac{1}{10} + \frac{1}{20} + \frac{1}{10} = \frac{5}{20} = \frac{1}{4} h r

= 15 m i n u t e s

Now, Average Speed

= \frac{T o t a l D i s t a n c e}{T o t a l T i m e}

= \frac{5}{0.25}

=20 km/hr

Question 16. Person A is traveling at 60 km/hr whereas person B is traveling at 25 m/s. Who is faster? [2 MARKS]

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Calculation: 1 Mark
Result: 1 Mark
Speed of Person B = 25 m/s

= 25 \times \frac{18}{5}

= 90 km/hr
Speed of Person A is 60 km/hr
Hence, Person B is faster.

Question 17. Explain uniform motion with the help of an example. [3 MARKS]

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Definition: 2 Marks
Example: 1 Mark
If a body is undergoing uniform motion, it implies that the body would be moving at a constant speed for the duration of motion. It will cover equal distances in identical intervals of time.
The second's hand of a clock undergoes uniform motion since it covers the exact same distance in each and every second.

Question 18. A car covers 20 km in the first hour and 30 km in the last 4 hours. Find:
i) Speed of car in the first hour
ii) Speed of the car in the last four hours
iii) Average speed of the car [3 MARKS]

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Each part: 1 Mark
i) Speed of the car in the first hour

= \frac{D i s t a n c e}{t i m e}

= \frac{20}{1} \frac{k m}{h r}

= 20 km/hr
ii) Speed of the car in the last 4 hours

= \frac{D i s t a n c e}{t i m e}

= \frac{30}{4} \frac{k m}{h r}

= 7.5 km/hr
iii) Total distance covered = 20 + 30 = 50 km
Total time taken = 1 + 4 = 5 hrs
Average speed

= \frac{T o t a l D i s t a n c e}{T o t a l t i m e} = \frac{50}{5}

= 10 km/hr

Question 19. Calculate:
(i) Seconds in a day
(ii) Minutes in a week
(iii) Hours in a year [3 MARKS]

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Sub-parts: 1 Mark each
(i) Seconds in a day

= 60 \times 60 \times 24 = 86400 s e c o n d s

(ii) Minutes in a week

= 60 \times 24 \times 7 = 10080 m i n u t e s

(iii) Hours in a year

= 24 \times 365 = 8760 h o u r s

Question 20. A body covers 3 km in 10 min, 6 km in 30 min and 10 km in 60 min. Is the motion of the body uniform? [2 MARKS]

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Condition for uniform motion: 1 Mark
Answer: 1 Mark
Speed1

= \frac{3}{10} = 0.3 k m / m i n

Speed2

= \frac{6}{30} = 0.2 k m / m i n

Speed3

= \frac{10}{60} = 0.166 k m / m i n

When a body is in a uniform motion, it covers equal distance in equal intervals of time.
In the above question, speed in all the three cases is different. Hence,it is not a uniform motion.