# Help on a rather simple physics question

## Homework Statement

Suppose you drop a feather and a steel ball of equal masses (0.014 kg) at the same time from a height of 1.5 m and you are told that the feather hits the floor 3.5 s after the steel ball. Estimate the value of the terminal velocity of the feather in air.

Estimate the feather's drag coefficient.

v=mg/c

## The Attempt at a Solution

I assumed the drag on the steel ball is negligible. So i used r=vit +.5at^2 to find the time it takes for it reach the ground. I then added 3.5s and used another kinematic equation to find the final velocity or terminal velocity. I then plugged the answer into the above equation to find c. it was wrong

## Answers and Replies

Simon Bridge
Science Advisor
Homework Helper
What does the v-t graph of the feather look like?
i.e. do the kinematic equations even apply to it's motion?

Consider: if the air-resistance for the steel ball can be neglected - so it never reaches it's terminal velocity - then what is the case for the feather? How long does it take the feather to reach it's terminal velocity?

Chestermiller
Mentor
Assume that the feather reaches its terminal velocity instantaneously. How far did it fall? How many seconds did it take to fall this distance? What was its velocity?