The first three energy levels of the fictitious element X were shown in Figure P38.54. An electron with a speed of 1.4×10⁶ m/s collides with an atom of element X. Shortly afterward, the atom emits a photon with a wavelength of 1240 nm. What was the electron’s speed after the collision? Assume that, because the atom is much more massive than the electron, the recoil of the atom is negligible. Hint: The energy of the photon is not the energy transferred to the atom in the collision.

On a frictionless air hockey table, puck A of mass 0.250 kg moves to the right and collides with puck B of mass 0.38kg, which is initially at rest. After the collision, puck A is moving the left at 0.12 m/s and puck B moves to the right at 0.65 m/s. What was the initial velocity of puck A before the collision?

A 110-kg tackler moving at 2.5 m/s meets head-on (and holds on to) an 82-kg halfback moving at 4.4 m/s. What will be their mutual speed immediately after the collision?

A 22-g bullet traveling 240 m/s penetrates a 2.0-kg block of wood and emerges going 130 m/s. If the block is stationary on a frictionless surface when hit, how fast does it move after the bullet emerges?

Object A moves at 10 m/s at 53° and Object B moves at 5 m/s at –37° as shown below. Calculate the magnitude of the system's total momentum if both objects have a mass of 2kg.

On a frictionless air hockey table, puck A of mass 0.250 kg moves to the right and collides with puck B of mass 0.38kg, which is initially at rest. After the collision, puck A is moving the left at 0.12 m/s and puck B moves to the right at 0.65 m/s. What was the initial velocity of puck A before the collision?