Question

A car acquire a velocity of 72km/h in 10 sec starting from rest. Find acceleration

Answer 1

72 multiply by 5/18 to convert into m/s.
Velocity = 20 m/s
Time = 10 second
Acc a = v-u /t

Answer 2

Answer:

Given Question :

A car moves with a velocity of 72km/hr. It is brought to rest in10s.

To Find :

(i) The velocity in m/s

(ii) The retardation

Important Formulae :

$v = u + at$

$s = ut + \frac{1}{2} a {t}^{2}$

$2as = {v}^{2} - {u}^{2}$

Here,

u is initial velocity

v is final velocity

s is distance covered

t is time taken

a is the acceleration

Solution :

Velocity is defined as the displacement by a body per unit time. It is expressed in km per hour or m per second.

Acceleration is the rate of change of velocity with respect to time. It is expressed in kmh¯² or ms¯².

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(i)Velocity in m/s :

For the conversion of velocity in kmh¯¹ into ms¯¹, we multiply 5/18,

So,

1 kmh¯¹ = 5/18 ms¯¹

72 kmh¯¹ = 5/18×72 = 20 ms¯¹.

Hence, velocity of car is 20 ms¯¹.

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(ii)Retardation of car:

u = 20 ms¯¹

v = 0 ms¯¹

t = 10 sec

$→v = u + at \\ →0 = 20 + a \times 10 \\→ - 20 = 10 \times a \\ → - \frac{20}{10} = a \\→ - 2 \: m {s}^{ - 2} = a$

Therefore, the Retardation of the car is 2 ms¯².