Question

part a. A penny falls, from rest, from a high window, and accelerates downwards because of gravity. How much time will pass before the velocity of the penny is -15.0 m/s? part b. How far will the penny have fallen at this time?

Answer 1

Given:

the penny falls from rest.

The final speed of the penny is,

`v=-15.0\text{ m/s}`

To find:

The time taken by the penny

the distance covered by the penny in this time

Step-by-step explanation:

a)

Let, the time be t.

We can write,

`v=u+gt`

substituting the values we get,

`\begin{gathered} -15.0=0-9.8* t \\ t=(15.0)/(9.8) \\ t=1.53\text{ s} \end{gathered}`

Hence, the required time is 1.53 s.

b)

In this time time the penny falls,

`\begin{gathered} h=-(1)/(2)gt^2 \\ =-(1)/(2)*9.8*1.53^2 \\ =-11.5\text{ m} \end{gathered}`

Hence, the penny had fallen 11.5 m downward.