13. MOTION AND TIME
1. Classify the following as motion along a straight line, circular or oscillatory motion:
(i) Oscillatory motion
(ii) Motion along a straight line
(iii) Circular motion
(iv) Oscillatory motion
(v) Oscillatory motion
(vi) Motion along a straight line
2. Which of the following are not correct?
(i) Correct
(ii) incorrect
(iii) Correct
(iv) Correct
(v) incorrect
3. Time period of the pendulum = Number of oscillations = 20 = 0.625 oscillations/second
Total time taken
32
4. Speed = Distance = 240
= 60 km/hr
Time
4
5. Distance traveled by the car at 8:50 AM = 57336 – 57321 = 15 km
Speed of the car (in km/min) = 15 = 0.75 km/min
20
Speed of the car (in km/h) =
15
= 15 X 60 = 900 = 45 km/h
20
20
20
60
6. Time taken by Salma to reach her school = 15 minutes = 15 X 60 seconds = 900 seconds
Speed of Salma while riding her bicycle = 2 m/s
Distance = speed X time = 2 X 900
=
1800 m = 1.8 km
7. Show the shape of the distance-time graph for the motion in the following cases:
(i) car moving with a constant speed
Distance
(ii) car parked on a side road
Distance
Time
time
8. (ii) Speed = Distance
Time
9. (iv) m/s
10. (ii) 25 km
( Solution: Distance traveled by the car in first 15 minutes = speed X time
= 40 X 15
60
= 10 km
Distance traveled by the car in next 15 minutes = speed X time
= 60 X 15
60
= 15 km
Total distance covered by the car in 30 minutes = 10 + 15 = 25 km)
11. If the distance covered by the blue car in 10 s is 100m then its speed will be
= 100/10
= 10 m/s
12. Vehicle A is moving faster as it has covered more distance than vehicle B in same time.
13. Graph (iii) is shows a truck which is not moving with constant speed.