Question

An object moving with speed of 36kmph attains a speed of 72kmph in 0.5 seconds. Find :d in 5 seconds. force if it weighs 100mg.​

Answer 1

✦ Question ✦

An object moving with speed of 36kmph attains a speed of 72kmph in 0.5 seconds. Find : (I) displacement in 5 seconds. (II) force on the object if it weighs 100gm.

$\Large{\underline{\underline{\bf{Answer:-}}}}$

$\large{\boxed{\bold{Displacement\:=\:d\:=\:75\:m}}}$

$\underline{\boxed{\textsf{F = {\textbf{0.2N}}}}} \qquad\qquad \bigg\lgroup\bold{Force \ on \ Object} \bigg\rgroup$

Given:-

u = 36km/h

v = 72km/h

t = 5 s

Where,

U = " Initial Velocity "

V = " Final Velocity "

T = " Time Taken "

Have to Find:-

(I) Displacement in 5 seconds.

(II) Force on the object if it weighs 100g.

Calculations :-

Converting the values in m/s first .

u = 36×5/18

= 10m/s

v = 72×5/18

= 20m/s

Now , Let's find out acceleration .

For it we apply the 1st Equation of motion i.e,

$\large{\boxed{\bold{v\:=\:u + \: at}}}$

Then , putting up the values it the above equation :-

A = v - u / t

" A " = Acceleration

" v " = Final Velocity

" u " = Initial Velocity

"T " = Time Taken

↠ 20 = 10 + a×5

↠ 20-10 = a × 5

↠ 10 = a×5

↠ a = 10/5

↠ a = 2m/s²

We got Acceleration as 2m/s²

Just find out the displacement directly by using the 3rd equation of motion

↠ v² = u² +2as

Again put up the values :-

↠ 20² = 10² + 2× 2 × s

↠ 400 = 100 + 4×s

↠ 400-100 = 4×s

↠ 300 = 4× s

↠ s = 300/4

↠ s = 75m

$\large{\boxed{\bold{D\:=\:75\:m}}}$

Thereby ,

Find out force now ,

Force = Mass of Object × Acceleration

F = ma

As according to the Question :-

↠ 0.1 × 2 { 1kg = 1000gm = 0.1 kg }

↠ Force = 0.2 Newton

More related information :-

✮ First equation of motion

❥ v = u + at.

v = final velocity.

u = initial velocity.

a = acceleration.

t = time taken.

Note :

First equation of motion also called velocity time equation.

✮ Second equation of motion

↠ s = ut + ½ at².

u = initial velocity.

a = acceleration.

t = time taken.

s = distance covered.

Note :-

Second equation of motion also called positive time equation.

✮ Third equation of motion

❥ v² - u² = 2as

v = final velocity.

u = initial velocity.

a = acceleration.

Note :-

Third equation of motion also called velocity positive equation.

❥ First law of motion

↠ First law of motion states that an object continues to be in a state of rest or of uniform motion along a straight line unless acted upon by an unbalanced force.

❥ Second law of motion

↠ Second law of motion states that the rate of change of momentum of an object is proportional to the applied unbalanced force in the direction of the force.

❥ Third law of motion

↠ Third law of motion states that for every action there is an equal and opposite reaction and they act on two different bodies.

Answer 2

Given:-

u = 36km/h

v = 72km/h

t = 5 s

Where,

U = " Initial Velocity "

V = " Final Velocity "

T = " Time Taken "

Have to Find:-

(I) Displacement in 5 seconds.

(II) Force on the object if it weighs 100g.

Calculations :-

Converting the values in m/s first .

u = 36×5/18

= 10m/s

v = 72×5/18

= 20m/s

Now , Let's find out acceleration .

For it we apply the 1st Equation of motion i.e,

\large{\boxed{\bold{v\:=\:u + \: at}}}

v=u+at

Then , putting up the values it the above equation :-

A = v - u / t

" A " = Acceleration

" v " = Final Velocity

" u " = Initial Velocity

"T " = Time Taken

↠ 20 = 10 + a×5

↠ 20-10 = a × 5

↠ 10 = a×5

↠ a = 10/5

↠ a = 2m/s²

We got Acceleration as 2m/s²

Just find out the displacement directly by using the 3rd equation of motion

↠ v² = u² +2as

Again put up the values :-

↠ 20² = 10² + 2× 2 × s

↠ 400 = 100 + 4×s

↠ 400-100 = 4×s

↠ 300 = 4× s

↠ s = 300/4

↠ s = 75m

\large{\boxed{\bold{D\:=\:75\:m}}}

D=75m

Thereby ,

Find out force now ,

Force = Mass of Object × Acceleration

F = ma

As according to the Question :-

↠ 0.1 × 2 { 1kg = 1000gm = 0.1 kg }

↠ Force = 0.2 Newton