Final answer:
The claim that all aircraft can land on slopes between 8 and 15 degrees is false; capabilities depend on specific factors. The statement about a rock's kinetic and potential energy during its flight is false; energy conversions occur as the rock moves.
Step-by-step explanation:
The statement that 'all aircraft can land if the ground slope is between 8 and 15 degrees' is false. The capability of an aircraft to land on a particular slope depends on many factors such as the type of aircraft, landing gear design, pilot skill, and the aircraft's performance characteristics. Commercial passenger jets typically require a much gentler slope, close to level ground, while some military aircraft and specially designed bush planes may be able to handle rougher and steeper terrain.
When discussing the energy changes of a rock thrown into the air, it is false that its kinetic energy increases with height. As the rock rises, its kinetic energy actually decreases due to loss of speed, and its potential energy increases. Conversely, as it falls back to the ground, the potential energy decreases, and the kinetic energy increases as the rock's velocity increases.
The statement about friction—that it 'varies from surface to surface because different substances have different degrees of roughness or smoothness'—is true. This concept is fundamental in the study of physics, specifically in mechanics, where frictional forces are essential for understanding the motion of objects.
Regarding kinetic friction, it's true that it is generally less than the limiting static friction. Once an object starts moving, the static friction is overcome, and the kinetic friction, which is less, takes over. This makes it easier to keep an object moving than to start moving it from rest.
For the plane coming in for a landing, the kinetic energy will 'decrease, 40 kN' due to the net force acting rearward, opposing the motion and causing the aircraft to lose speed.
Inclination of ground such as in the scenario of a snowboarder gliding down a slope that is inclined at 13° illustrates how angles and slopes can affect movement and frictional forces. Understanding these interactions is key to physics and engineering applications, including flight and landing of aircraft, as well as many other real-world activities.