Final answer:
The question deals with physics concepts of energy conversion on a frictionless hill, conservation of momentum in a collision, and the effects of friction on the motion of sleds. It involves conservation of energy, momentum, and Newton's laws of motion to analyze different scenarios in which a sled is the primary object of study.
Step-by-step explanation:
The student's question pertains to concepts from physics related to the motion of objects under the influence of gravity and, specifically, the conservation of energy and momentum. When a sled slides without friction down an ice-covered hill, starting from rest and reaching a speed of 6.5 m/s at the bottom, this is an example of potential energy being converted to kinetic energy. For other scenarios described, such as objects being thrust horizontally on a frictionless surface or the elastic collision between a sled and a boulder, the conservation of linear momentum is also involved.
For the frictionless descent of the sled, we use the conservation of mechanical energy, where the potential energy at the top is equal to the kinetic energy at the bottom. In situations involving collisions, the conservation of momentum is used to determine the velocities after the collision, taking into account the masses of the objects involved.
In the presence of friction, such as a sled being pulled across snow, we would look at forces, acceleration, and the work-energy principle to resolve the questions. This involves calculating the net work done by friction and using Newton's second law to determine the force necessary to pull the sled at constant velocity.