Final answer:
The increased height of a thrown rock raises its potential energy, not kinetic energy, and the position vs time graph of a speeding object is curved, not straight. Additionally, the efficiency of a simple machine is always under 100% due to energy loss to friction.
Step-by-step explanation:
Understanding Kinetic and Potential Energy
Concerning the statement about a rock thrown into the air, it is false that the increase in height would increase the rock's kinetic energy. In fact, as the rock goes higher, its potential energy increases while its kinetic energy decreases. Conversely, as the rock falls back to the ground, its kinetic energy increases (due to its increasing velocity) and its potential energy decreases.
Understanding Motion Graphs
The position vs time graph for an object that is speeding up is false to be a straight line. Instead, the graph for an object with constant acceleration, which is speeding up, is a curved line, indicating that the velocity is changing over time.
Concept of Efficiency in Machines
The statement that the efficiency of a simple machine is always less than 100 percent is true. This is due to the fact that some portion of the input work is always lost to friction, which typically converts to heat energy, preventing any machine from being perfectly efficient.