Question

A car starting from rest acquires a velocity of 72km/h in 10s. find its acceleration.​

Answer 1

$\bold\Solution$

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 + atv=u+at

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

2

1

at

2

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

__________________________________________

(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.

__________________________________________

(ii)Retardation of car:

u = 20 ms¯¹

v = 0 ms¯¹

t = 10 sec

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

→v=u+at

→0=20+a×10

→−20=10×a

→−

10

20

=a

→−2ms

−2

=a

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

Answer 2

Answer:

$\huge \fbox \red{answer}$

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 + atv=u+at

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

2

1

at

2

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

__________________________________________

(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.

__________________________________________

(ii)Retardation of car:

u = 20 ms¯¹

v = 0 ms¯¹

t = 10 sec

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

→v=u+at

→0=20+a×10

→−20=10×a

→−

10

20

=a

→−2ms

−2

=a

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