 # Speed

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• Q1

Write down the differences between uniform and non - uniform motion.

Marks:3

 Uniform motion Non – Uniform motion In this motion, a moving body covers equal distance in equal time intervals. In this motion, a moving body covers unequal distance in equal time intervals. A body maintains the same speed throughout the motion. A body does not maintains the same speed throughout the motion. For example: Motion of the vehicle moving with same speed without stopping. For example: Motion of a bus starting from a depot.

• Q2

A train travels at a speed of 60 km/hr for 0.52hr, at 30 km/h for the next 0.24 hr and then at 70 km/h for the next 0.71h.What is the average speed of the train?

Marks:5

i) In the first case, the train travels at a speed 0f 60km/h for a time of 0.52h.
Now, speed = distance / time = 60 km/h

Distance = 60 x 0.52 = 31.2 km ------------------------- (1)

ii) In the second case, the train travels at a speed 0f 30km/h for a time of 0.24h.

Now, speed = distance / time = 30 km/h

Distance = 30 x 0.24 = 7.2 km ------------------------------- (2)

iii) In the third case, the train travels at a speed of 70km/h for a time of 0.71h.
Now, speed = distance / time = 70 km/h
Distance = 70 x 0.71 = 49.7 km ------------------------------- (3)

From equation 1, 2 & 3 we get,

Total distance travelled = (31.2 + 7.2 + 49.7) km = 88.1 km.

Total time taken =(0.52 + 0.24 + 0.71)h = 1.47 h. average speed = Total distance travelled / totala time taken

= (88.1/1.47)km/h

Hence, average speed = 59.9 km/h

• Q3

A bus between Vishakhapatnam and Hyderabad passed the 100 km, 160 km and 220 km points at 10.30 a.m., 11.30 a.m. and 1.30. p.m. Find the average speed of the bus.

Marks:3

a) The distance covered between 10.30. a.m. and 11.30 a.m. = 160 km - 100 km = 60 km
The average speed during this interval is,

Average speed (v1) = distance / time taken
or, v1 = 60 km/hr
b) The distance covered between 11.30. a.m. and 1.30p.m. = 220 km - 160 km = 60 km

The average speed during this interval is,

v2 = distance / time taken

or, v2 = 60 km/2h = 30 km/h

c) The distance covered between 10.30. a.m. and 1.30p.m. = 220 km -100 km = 120 km

The average speed during this interval is,

v3 = distance / time taken

or, v3 = 120 km/3 hr = 40 km/h

• Q4

Convert speed of 72km/hr into
a) m/s
b) cm/s

Marks:2

a) In m/s,
Speed = 72 km/hr
= 72 x [(1000 m) / (60 x 60 s)]
= 20 m/s
b) In cm/s,
1m = 100cm
Speed = 72 km/hr = 20 m/s
= 20 (100cm) / 1 s
= 2000 cm/s

• Q5

Define the following
a) Average speed
b) Uniform speed.

Marks:2