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 .

Step-by-step 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 = (1)/(2)mv^2` , where m is mass & v is the velocity of object !

By conservation of energy :

⇒
`P.E.=K.E`

⇒
`mgh=(1)/(2) mv^2`

⇒
`v=√(2gh)`

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

⇒
`v=√(2(9.8)20)`

⇒
`v=√(392)`

⇒
`v=19.80m/s`

Hence , Speed of ball is 19.80 m/s .