Question

What is the velocity of a body of mass 5 kg starts from rest, if a force of 10 N acts on the body for 10 seconds? ​

Answer 1

Understanding the question: This question says that we have to find out the final velocity of a body whose mass is 5 kilograms and it starts from the rest and the force of 10 Newton acts on the body for 10 seconds. Let's do it!

GivEn that:

• Force = 10 Newton
• Initial velocity = 0 m/s
• Mass = 5 kilograms
• Time = 10 seconds

Don't be confused! Initial velocity came as zero because the body starts from rest.

To calculAte:

• The final velocity

SoluTion:

• The final velocity = 20 m/s

UsiNg formula:

${\small{\underline{\boxed{\pmb{\sf{F \: = m \cdot \dfrac{(v-u)}{t}}}}}}}$

Where, F denotes force , m denotes mass , v denotes final velocity , u denotes initial velocity and t denotes time.

Full SolutioN:

$:\implies \sf F \: = m \cdot \dfrac{(v-u)}{t} \\ \\ :\implies \sf 10 = 5 \cdot \dfrac{(v-0)}{10} \\ \\ :\implies \sf 10 = 5 \cdot \dfrac{v}{10} \\ \\ :\implies \sf 10 = \dfrac{v}{2} \\ \\ :\implies \sf 10 \cdot 2 = \: v \\ \\ :\implies \sf 20 \: = v \\ \\ :\implies \sf v \: = 20 \: m/s \\ \\ :\implies \sf Final \: velocity \: = 20 \: m/s$

AdditioNal information:

➟ Newton's law of motion -Newton if the father of physics and he established the laws of motion in his book named ❛Principia❜ in the year 1667.

➟ Newton's first law of motion - Every body maintain it's maintain it's initial state of rest or motion with uniform speed on straight line unless an external force act on it.

◆ It's also known to be law of Galileo or law of inertia.

• Law of inertia = It is the property of a body by virtue of which the body opposes change in it's initial state of rest or motion with uniform speed on a straight line. There are 2 types of inertia –

⑴ Inertia of rest

⑵ Inertia of motion

Some examples of inertia –

⑴ When a coat /blanket is beaten by a stick the dust particles are removed.

⑵ When a car start suddenly the passenger bends backwards.

◆ Important - First law gives the definition of force.

• Force - It is that external cause which when acts on a body changes or tries to change the initial state of the body.

• Momentum - It is that property of a moving body and is defined of mass and velocity of the body. It's a vector quantity. SI unit is kg m/s

$\: \: \: \: \: \: \:{\sf{Momentum = \: Mass \times Velocity}} \: \: \green\star$

➟ Newton's 2nd law of motion - The rate of change in momentum of a body is directly proportional to the applied force on the body and take place in the direction of force.

If f = force applied ; a = acceleration produced and m = mass of body the nF = ma.

◆ Newton's second law gives the magnitude of force.

◆ Newton's first law is contained in the second law.

➟ Newton's 3rd law of motion - To every action there is an equal and opposite reaction.

Some examples -

⑴ Motion of the rocket.

⑵ Recoil of the gun.