Kevin S. Huang

2011: Problem 14

Topic: Kinematics
Concepts: Free fall

Solution:

From kinematics, we have

h=\frac{1}{2}gt^2 \propto t^2

where $h$ is the height an object is dropped and $t$ is the time it takes to reach the ground.

Suppose the first ball above the ground at height $h_1$ takes time $T$ to hit the floor. We want to find the height of the $n$ th ball so that it takes time $nT$ to hit the floor. Since $h \propto t^2$ ,

\frac{h_1}{T^2}=\frac{h_n}{(nT)^2}

h_n=n^2h_1

so the balls should be placed at square multiples of the first height. Thus, the answer is D.

PDF

Kevin S. Huang

2011: Problem 14

Like this:

Leave a ReplyCancel reply

2011: Problem 14

Like this:

Leave a ReplyCancel reply

Discover more from Kevin S. Huang