Question

Guys please tell the answer fast I have to recheck my answer
and Pray for me I have Physics Exam Tomorrow​

Answer 1

Question :-

A force of 100 N acts on an object of mass 10 kg for 9 sec. If the object was initially moving with the speed of 10 m/s, calculate the initial and final kinetic energy of the object. By what factor does the Kinetic energy increase?

Solution :-

We will find the acceleration first.

From Newton's second law of motion, we know that

F = ma

Substitute the values,

→ 100 = 10a

→ a = 100/10

→ a = 10 m/s²

Now, initial velocity, u = 10 m/s and time, t = 9 sec. We have to find final velocity, v

From first equation of motion we know,

v = u + at

→ v = 10 + 10(9)

→ v = 10 + 90

→ v = 100 m/s

Now, kinetic energy = 1/2 × mv²

So, initial kinetic energy =

1/2 × 10 × (10)²

→1/2 × 10 × 100

→ 500 Joules.

Final kinetic energy = 1/2 × mv²

1/2 × 10 × (100)²

→ 1/2 × 10 × 10000

→ 50,000 Joules

Now, the factor by which kinetic energy increased = 50,000/500 = 100

So, the final Kinetic energy became 100 times of the initial.

Answer 2

Hey best of luck . Even I have physics ICSE tomorrow !

Best wishes :)

Question :

A force of 100 N acts on an object of mass 10 kg for 9 sec. If the object was initially moving with the speed of 10 m/s, calculate the initial and final kinetic energy of the object. By what factor does the Kinetic energy increase?

Solution :

Given that force acting on the body is 100 N .

Mass is given 10 kg .

Find the acceleration

$Force=mass\times acceleration\\\\\implies acceleration=\frac{force}{mass}\\\\\implies a=\frac{100N}{10m}\\\\\implies a=10m/s^2$

Find the final velocity

Intial velocity given is 10 m/s

Final velocity is not given .

By Laws of Motion :

v = u + a t

⇒ v = 10 m/s + 10 m/s² × 9 s

⇒ v = 10 m/s + 90 m/s

⇒ v = 100 m/s

The final velocity is 100 m/s

Find the initial kinetic energy

Initial kinetic energy = $\frac{1}{2}mu^2$

$\implies \frac{1}{2}\times 10kg\times 10m/s\times 10m/s\\\\\implies \frac{1}{2}\times 1000J\\\\\implies 500J$

Find the final kinetic energy

Final kinetic energy = $\frac{1}{2}mv^2$

$\implies \frac{1}{2}\times 10kg\times (100m/s)^2\\\\\implies \frac{1}{2}\times 10\times 10000 J\\\\\implies 50000 J$

Find the factor

$\mathtt{Factor\:of\:increase=\frac{final\:kinetic\:energy}{initial\:kinetic\:energy}}\\\\\implies \frac{50,000J}{500}\\\\\implies 100$