Question

A car decreases its speed from 80 km/h to 60 km/h in 5 seconds. Find the acceleration of the car.

Answer 1

Explanation:

here's your answer

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Answer 2

Given:

A car decreases its speed from 80 km/h to 60 km/h in 5 seconds

To Find:

Acceleration of the car

Solution:

We know that,

• First equation of motion is

⟼ $\pink{\boxed{\bf{v=u+at}}}$

where,

• v is final speed
• u is initial speed
• a is acceleration
• t is time taken

Now, here

$\sf{Initial\:Speed,u=80\:km/h=80\times\dfrac{5}{18}m/s=\dfrac{200}{9}m/s}$

$\sf{Final\:Speed,v=60\:km/h=60\times\dfrac{5}{18}m/s=\dfrac{150}{9}m/s}$

Time taken,t= 5 sec

Now, on applying first equation of motion, we get

$\longrightarrow\mathrm{\dfrac{150}{9}=\dfrac{200}{9}+a(5)}$

$\longrightarrow\mathrm{\dfrac{150}{9}-\dfrac{200}{9}=a(5)}$

$\longrightarrow\mathrm{\dfrac{150-200}{9}=5a}$

$\longrightarrow\mathrm{\dfrac{-50}{9}=5a}$

$\longrightarrow\mathrm{\cancel{5}a=\dfrac{\cancel{-50}}{9}}$

$\longrightarrow\mathrm{a=\dfrac{-10}{9}=-1.11\:m/s^{2}}$

Hence, car decelerated from 80km/h to 60 km/h with the rate of -1.11 m/s².