Question

a body decreases its speed from 50 m/s to 10 m/s in 10s.
what is its acceleration?

Answer 1

Answer: -4 m/s²

Explanation:

initial velocity (u)=50 m/s

final velocity (v)=10 m/s

time (t)=10s

acceleration=change in velocity/time

a=v-u/t

a=10-50/10

a=-40/10

a=-4 m/s²

Answer 2

Answer:

• Acceleration is -4 m/s².

Given:

• Initial velocity = 50 m/s
• Final velocity = 10 m/s
• Time taken = 10 sec

Explanation:

$\rule{300}{1.5}$

Here, we are given that a body decreases it's speed from 50 m/s to 10 m/s in 10 sec. We are asked to find it's acceleration.

From first kinematic equation we know,

$\longrightarrow{\sf{v\ =\ u\ +\ at}}$

Here,

• v denotes final velocity
• u denotes initial velocity
• a denotes acceleration
• t denotes time taken

Substitute the values,

$\longrightarrow{\sf{10\ =\ 50\ +\ a \times 10}} \\ \\ \\ \longrightarrow{\sf{10\ =\ 50\ +\ 10a}} \\ \\ \\ \longrightarrow{\sf{10\ -\ 50\ =\ 10a}} \\ \\ \\ \longrightarrow{\sf{-40\ =\ 10a}} \\ \\ \\ \longrightarrow{\sf{\dfrac{-40}{10}\ =\ a}} \\ \\ \\ \longrightarrow{\sf{-4\ =\ a}} \\ \\ \\ \longrightarrow{\sf{a\ =\ -4\ m/s^2}}$

∴ The acceleration of the body is -4 m/s² [Here, -ve sign shows retardation].

$\rule{300}{1.5}$