Question

If Phred throws a rock straight up, and Phran throws a rock straight up with twice the velocity of Pread's rock, how will the maximum height of Phred's rock compare to Phran's?

Answer 1

The maximum height of Phran stone is four time that of Phred stone

Step-by-step explanation:

From the question we are told that

The initial velocity of Phred stone is u

The initial velocity of Phran stone is 2u

Generally from kinematic equations

`v^2 = u^2 + 2(-g)h`

Here the negative sign shows that the direction of the stone is against gravity

At the maximum height v which is the final velocity of the stone is zero

So

`0 = u^2 - 2gh`

So for Phred stone the height attained is

=>
`h_1 = (u^2)/(2g)`

For Phran stone the height attained is

=>
`h_2 = ((2u)^2)/(2g)`

=>
`h_2 = (4u^2)/(2g)`

=>
`h_2 = 4 h_1`

Hence the maximum height of Phran stone is four time that of Phred stone