Question

Q.10) What force will change the velocity of a body of mass 1kg from 20 m/s
to 30 m/s in two sec..?
A) IN
B) 5N
C)10 N
D) 25 N​

Answer 1

Provided that:

• Mass of a body = 1 kg
• Initial velocity = 20 m/s
• Final velocity = 30 m/s
• Time = 2 seconds

To calculate:

• Force

Solution:

• Force = 5 N

Using concept:

• Force formula

Using formula:

• F = ma

Where, F denotes force, m denotes mass and a denotes acceleration.

Knowledge required:

•️ We can calculate the SI unit of force by using the SI units o mass and acceleration. The SI unit of mass is kg and the SI unit of acceleration is m/s² Therefore, the SI unit of force is kg · m/s² that is kg m/s² But to the honour of Sir Issac Newton the SI unit of force becames Newton(N)

Required solution:

$:\implies \sf Force \: = mass \times acceleration \\ \\ :\implies \sf F \: = m \times a \\ \\ :\implies \sf F \: = ma \\ \\ \sf From \: the \: formula, \\ \\ :\implies \sf F \: = m \times \dfrac{v-u}{t} \\ \\ :\implies \sf F \: = 1 \times \dfrac{30-20}{2} \\ \\ :\implies \sf F \: = 1 \times \dfrac{10}{2} \\ \\ :\implies \sf F \: = 1 \times \cancel{\dfrac{10}{2}} \\ \\ :\implies \sf F \: = 1 \times 5 \\ \\ :\implies \sf F \: = 5 \: N \\ \\ :\implies \sf Force \: = 5 \: Newton$

Additional information:

$\begin{gathered}\boxed{\begin{array}{c|cc}\bf Distance&\bf Displacement\\\frac{\qquad \qquad \qquad\qquad\qquad \qquad\qquad\qquad}{}&\frac{\qquad \qquad \qquad\qquad\qquad \qquad\qquad\qquad}{}\\\sf Path \: of \: length \: from \: which &\sf The \: shortest \: distance \: between \\ \sf \: object \: is \: travelling \: called \: distance. &\sf \: the \: initial \: point \: \& \: final \\ &\sf point \: is \: called \: displacement. \\\\\sf It \: is \: scalar \: quantity. &\sf It \: is \: vector \: quantity \\\\\sf It \: is \: positive \: always &\sf It \: can \: be \: \pm \: \& \: 0 \: too \end{array}}\end{gathered}$

Answer 2

Given:-

• Initial velocity ,u = 20m/s
• Final Velocity ,v = 30m/s
• Time taken ,t = 2s

To Find:-

• Force ,F

Solution:-

According to the Question

Firstly we calculate the acceleration of the body .

As we know that acceleration is defined as the rate of change in velocity.

• a = v-u/t

where,

• v is the final velocity
• a is the acceleration
• u is the initial velocity
• t is the time taken

Substitute the value we get

$\longrightarrow$ a = 30-20/2

$\longrightarrow$ a = 10/2

$\longrightarrow$ a = 5m/s²

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Now, Calculating the force acting .

Force is calculated by the product of mass & acceleration.

• F = ma

where,

• F denote Force
• m denote Mass
• a denote acceleration

Substitute the value we get

$\longrightarrow$ F = 1×5

$\longrightarrow$ F = 5 N

• Hence, the force is 5 newton.

So, the required answer is (B) 5 N

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━