Question

Plz solve question number 2,3,5,7,8
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Answer 1

2)

u = 10m/s

a = 5m/s^2

t = 5s

Using the equation of motion,

s = ut +1/2at^2

s = 10 × 5 + 0.5 × 5 × 25

s = 50 + 62.5

s = 112.5m

3)

At the first time period of 2s,

u = 30km/h = 8.333m/s

v = 33.6km/h = 9.333m/s

t = 2s

So, by using the equation of motion v = u + at

a = (v-u)/t

a = 1/2

a = 0.5m/s^2

Since, the velocity is increasing at a constant rate of 3.6km/h for every equal time interval, this is a uniformly accelerated motion.

5)

Here, u = 20m/s

v = 0m/s (Since it comes to rest)

s = 10cm = 0.1m

Using the equation of motion, v^2 - u^2 = 2as

a = -400/0.2

a = -2000m/s^2

That is retardation = 2000m/s^2

7)

(i) Here, v1 = 60km/h, v2 = 80km/h

So, the average speed is given by the formula, 2v1v2 ÷ ( v1 +v2)

= 2 × 60 × 80 ÷ 140

= 68.57km/h

(ii) Since it's displacement is zero because it is returning to the same point, it's average velocity will be equal to zero.

8)

(i) Here, u = 90km/h = 25m/s

a = -0.5m/s^2

t = 10s

Using the equation of motion, v = u + at

v = 25 - 0.5 × 10

v = 25 - 5

v = 20 m/s

(ii)

Here v = 0 m/s (at rest)

So, t = u/a

t = 25 ÷ 0.5

t = 50s

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