A spaceship leaves Earth and maintains a constant force by means of a nuclear engine. As the speed of the spaceship increases, an observer on Earth finds that relative to her the magnitude of the spaceship's acceleration is
A) 0.
B) decreasing.
C) constant.
D) increasing.
E) proportional to the kinetic energy of the spaceship.

Question

Quizplus · Accepted Answer

As the spaceship's speed increases, its mass effectively increases due to relativistic effects (according to the theory of relativity). Since acceleration is force divided by mass (a = F/m), and the force remains constant while the effective mass increases, the acceleration observed from Earth decreases.

A Spaceship Leaves Earth and Maintains a Constant Force by Means