A budding magician holds a 2.24-mW laser pointer, wondering whether he could use it to keep an object floating in the air with the radiation pressure. This might be an idea for a new trick! Assuming the laser pointer has a circular beam 3.00 mm in diameter and the magician rigs up a totally reflecting sail on which to shine the laser, what is the maximum weight the magician could suspend with this technique?

 W = 1.49 10⁻¹¹ kg

Explanation:

For this problem, let's use Newton's equation of equilibrium

           F - W = 0

            F = W              (1)

Strength can be found from the definition of pressure

        P = F / A

        F = P A

The radiation pressure for a reflective surface is

            P = 2 I / c)

We substitute in equation 1

         2 I / c  A = W

The intensity is defined by the ratio of the power between the area

          I = P / A

          P = I A

We substitute

          2 P / c = W

           W = 2  2.24 10-3 / 3 108

           W = 1.49 10⁻¹¹ kg

unbalanced force

explanation:

the aurora is formed when charged particles emitted from the sun during a solar flare penetrate the earth's magnetic shield and collide with atoms and molecules in our atmosphere. these collisions result in countless little bursts of light, called photons, which make up the aurora.

auroras are generated by charged solar particles hitting molecules in earth's atmosphere. this usually happens in high latitudes, because our planet’s magnetic field tends to funnel these particles toward the poles. that’s why it can be experienced in northern ohio.