Anucleus of radioactive radium (226ra), initially at rest, decays into a radon nucleus (222rn) and an alpha-particle (a 4he nucleus). if the kinetic energy of the alpha-particle is 6.72 × 10−13 j, what is (a) the recoil speed of the radon nucleus, and (b) its kinetic energy? the superscripts indicate, roughly, the mass of each nucleus in unified mass units (u), where 1 u = 1.66 × 10−27 k

In which scenario is the least amount of work done on a crate? a force of 120 n moves it 25 m. a force of 115 n moves it 26 m. a force of 130 n moves it 22 m. a force of 125 n moves it 27 m.

Unpolarized light of intensity i_0=750w/m^2 is incident upon two polarizers. after passing through both polarizers the intensity is i_2=280w/m^2. (a) what is the intensity of the light after it passes through the first polarizer in w/m^2? (b) write an equation for the angle between the polarizers in terms of the initial (i_0) and final (i_2) intensities. (c) find the angle between the polarizers in degrees.

Imagine that someone pushes one marble toward a motionless marble. would there still be action-reaction forces involved in the collision? how might the marbles’ motions be changed? ?