Classical Mechanics
# Introduction to Forces

A passenger in a closed train car moving at constant velocity tosses a coin directly upward. Where will the coin fall?

(Ignore effects of air resistance.)

Its popularity is due in part to the ease with which it can be modified to shoot faster and farther. One easy modification is to insert a secondary spring inside the main spring, as shown below:

If the strength (spring constant) of the first spring is \(k\), and the strength of the second spring is \(\frac12 k\), what is the strength of the two springs together?

**Details**

- Assume that there are no nearby stars to exert gravitational force on him.

One valid but counterintuitive answer is to jump out of the blender.

Suppose a person of height 1.80 m and mass 60 kg can jump to the height of 60 cm. If this person is shrunk to one thousandth of his original size, how high is he now able to jump in centimeters?

**Assumptions**

- The amount of power a human can generate is proportional to the muscle mass \(m\).

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