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

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 , 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 , where m is mass & v is the velocity of object !

By conservation of energy :

⇒

⇒

⇒

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

⇒

⇒

⇒

Hence , Speed of ball is 19.80 m/s .

snell's law

refractve index = sin incidence / sin refraction