When laser energy interacts with biologic tissue, the effect is influenced by:

Supernovae are one of the most extreme events in the known universe. They are caused by

As a blinking light source approaching you gains speed, you see the frequency of flashes

According to Alan Guth, magnetic monopoles are not observed in our universe because

A four dimensional image of a coffee table is depicted in a

A moving white hockey puck collides elastically with a stationary red hockey puck on a frictionless horizontal surface. No net external force acts on the two-puck system. Select all of the following statements that must be true for this collision.   (1) The kinetic energy of the white puck is conserved (same before and after the collision). (2) The linear momentum of the white puck is conserved. (3) The linear momentum of the two-puck system is conserved.

You and your friend are both standing on a horizontal frictionless surface. To get your friend’s attention, you throw a ball due west at your friend as shown below. The ball bounces elastically off your friend’s back. Which one of the following statements is true about this situation?  

A motorcycle and a truck are both moving in the same direction in adjacent lanes on a highway. At a particular instant, the speed of the motorcycle is four times as large as the speed of the truck v. At that instant, the motorcycle is accelerating forward while the truck is moving at a constant velocity. Which one of the following statements best describes which vehicle has a larger momentum at that instant?  

Two identical bullets are fired horizontally with identical speeds v0 at two blocks of equal mass. The blocks rest on a frictionless horizontal surface and are made of hard steel and soft wood respectively (see diagram below). One bullet bounces elastically off the steel block. The other bullet becomes embedded inside the wood block. Which one of the following statements best describes which block travels faster after the collision?

Carts A and B are identical in all respects before the collision.   Diagram (i): Cart A starts from rest on a hill at a height h above the ground. It rolls down and collides “head-on” with cart B which is initially at rest on the ground. The two carts stick together.   Diagram (ii): Carts A and B are at rest on opposite hills at heights h/2 above the ground. They roll down, collide “head-on” with each other on the ground and stick together.          Which of the following statements is true about the two-cart system just after the carts collide in the two cases?   Just after the collision,