Question

a 2.0kg ball is resting at the top of a 20 m hill. if the ball rolls down the entire hill, how fast will it be going?

Answer 1

Speed of ball is 19.80 m/s .

Explanation:

We have , a 2.0 kg ball is resting at the top of a 20 m hill. if the ball rolls down the entire hill,We need to find how fast will it be going.Let's find out:

We know that,

Potential energy : This is the energy possessed by an object due to it's virtue of height and is given by $P.E = mgh$ , where m is mass , g is acceleration due to gravity & h is height !

Kinetic energy : This is the energy possessed by an object due to it's virtue of motion and is given by $K.E = \frac{1}{2}mv^2$ , where m is mass & v is the velocity of object !

By conservation of energy :

⇒ $P.E.=K.E$

⇒ $mgh=\frac{1}{2} mv^2$

⇒ $v=\sqrt{2gh}$

According to question , h=20 m i.e.

⇒ $v=\sqrt{2(9.8)20}$

⇒ $v=\sqrt{392}$

⇒ $v=19.80m/s$

Hence , Speed of ball is 19.80 m/s .