Which of the following best describes a completely elastic collision? the kinetic energy (k) of the system before the collision equals k after. the potential energy (u) of the system before the collision equals u after. the kinetic energy (k) of the system before the collision is greater than k after. the kinetic energy (k) of the system before the collision is less than k after.,

The kinetic energy (K) of the system before the collision equals K after.

Explanation:

An elastic collision is a collision in which there is no net loss in kinetic energy from the system as a result of the collision. The amount of motion and the kinetic energy are conserved quantities in elastic collisions. This means that the kinetic energy (K) of the system before the collision equals K after.

Some collisions between atoms in gases are examples of perfectly elastic collisions.

d. air pressure decreases as altitude increases.

force is based upon mass and acceleration.the statement is not always true.

it can be explained from newton's second law of motion.

as per newton's second law of motion the rate of change of momentum is directly proportional to the applied force and takes place along the direction of force.

mathematically it can be written as -

                                              ⇒      

here   k is the proportionality constant whose value is 1.

                                                            [a is the acceleration=dv/dt]

hence we see that force not only depends on mass and acceleration but also on velocity and rate of change of mass. force f will depend on mass and acceleration only when mass is constant.

hence the statement that force is based upon mass and acceleration is false.