Question

A certain force acting on a 20kg mass changes it velocity from 5ms-'to 2ms-1...
can anyone please help me with this question?​

Answer 1

Correct Question :-

A certain force acting on a 20kg mass , it changes velocity from 5 m/s to 2m/s in 5s ,then find force acting .

Solution :-

Given ,

• Mass = 20kg
• Initial velocity = 5 m/s
• Final velocity = 2m/s

We need to find ,

• Force acting on the body = ?

Using newton's first law ,

• Force = mass × acceleration

Substituting acceleration = ( v - u ) / t

⇒ F = m ( v - u ) / t

⇒ F = 20 ( 2 - 5 ) / 5

⇒ F = 20 ( - 3 ) / 5

⇒ F = 4 ( - 3 ) / 1

⇒ Force = - 12 N

Here the force is negative . So, the body will move in the opposite direction , so Force = 12N .

Answer 2

Answer:

Correct Question :-

• A force acting on a 20 kg mass changes it velocity from 5 m/s to 2 m/s in 5 secs. Find how much force acting on it.

Given :-

• A force acting on a 20 kg mass changes it velocity from 5 m/s to 2 m/s in 5 secs.

To Find :-

• How much force acting on it.

Formula Used :-

We know that,

➣ F = ma

➣ a = $\dfrac{(v - u)}{t}$

Now, we substitute the formula we get,

$\boxed{\bold{\large{F\: =\: \dfrac{m(v - u)}{t}}}}$

where,

• F = Force
• m = Mass
• v = Final velocity
• u = Initial velocity
• t = Time taken

Solution :-

Given :

• Mass = 20 kg
• Initial velocity = 5 m/s
• Final velocity = 2 m/s
• Time = 5 secs

According to the question by using the formula we get,

⇒ F = $\dfrac{20(2 - 5)}{5}$

⇒ F = $\dfrac{20(- 3)}{5}$

⇒ F = $\dfrac{- 60}{5}$

⇒ F = $\sf\dfrac{\cancel{- 60}}{\cancel{5}}$

➠ F = - 12 N

We can't take force as negative. So force will be 20 N .

$\therefore$ The force acting on it is 12 N .