Question

14. A body of mass 5 kg is moving with a velocity of 10 m/s. It is acted upon by a force 20 N in
the direction of motion. What will be its velocity after 1 second?
​

Answer 1

Given :-

Mass of the body = 5 kg

Velocity of the body = 10 m/s

Force acted on the body = 20 N

To Find :-

The velocity of the body after 1 second.

Analysis :-

Here we are given with the mass, velocity and the force of the body.

Firstly find the acceleration of the body using it's respective formula.

Then substitute the values accordingly using the first equation of motion.

Solution :-

We know that,

• f = Force
• m = Mass
• a = Acceleration
• u = Initial velocity
• v = Final velocity
• t = Time

Using the formula,

$\underline{\boxed{\sf Force=Mass \times Acceleration}}$

Given that,

Force (f) = 20 N

Mass (m) = 5 kg

Substituting their values,

⇒ f = ma

⇒ 20 = 5 × a

⇒ a = f/m

⇒ a = 20/5

⇒ a = 4 m/s

Using the formula,

$\underline{\boxed{\sf First \ equation \ of \ motion=v=u+at}}$

Given that,

Initial velocity (u) = 10 m/s

Acceleration (a) = 4 m/s

Time (t) = 1 sec

Substituting their values,

⇒ v = 10 + (4 × 1)

⇒ v = 10 + 4

⇒ v = 14 m/s

Therefore, the velocity of the body after 1 second is 14 m/s.

Answer 2

$\large \underline{ \underline{ \sf \maltese \: {Given:-}}}$

• Mass (m) = 5 kg
• Initial Velocity (u) = 10m/s
• Force (f) = 20 N
• Time (t) = 1 sec

$\large \underline{ \underline{ \sf \maltese \: {To \: find:-}}}$

• Final velocity (v) = ?

$\large \underline{ \underline{ \sf \maltese \: {Solution:-}}}$

We know :–

$\qquad \bull \: \sf{f = m \times a}$

${:} \implies \sf{20 = 5a}$

${:} \implies \sf{5a = 20}$

${:} \implies \sf{a = \cancel \dfrac{20}{5 }}$

${:} \implies \boxed {\frak \red{a = 4}}$

$\qquad \therefore\: \underline{\sf{acceleration=4 \: m/s^2}}$

By the first equation of motion:–

$\qquad \bull \: \sf{ v = u + at}$

${:} \implies \sf{v = 10 + \bigg(4 \times 1 \bigg)}$

${:} \implies \sf{v = 10 +4 }$

${:} \implies \boxed{\frak \red{v = 14 \: m/s }}$

$\qquad \therefore\: \underline{\sf{final \: velocity=14 \: m/s}}$