Final answer:
During space shuttle liftoff, astronauts experience an acceleration of 1.4g, which means they feel a force 1.4 times greater than Earth's gravitational acceleration, equating to 13.72 m/s². Option C is correct.
Step-by-step explanation:
The acceleration value of 1.4g during space shuttle liftoff represents C) 1.4 times the gravitational acceleration on Earth's surface. This means that astronauts feel a force equal to 1.4 times their normal weight due to gravity. The acceleration due to gravity at Earth's surface, denoted as 'g', is 9.80 m/s². Therefore, during liftoff, the astronauts experience an acceleration of 1.4 × 9.80 m/s², which is about 13.72 m/s². This acceleration is what causes them to feel heavier during the ascent.
The acceleration value of 1.4g experienced by space shuttle astronauts during liftoff represents 1.4 times the gravitational acceleration on Earth's surface (option C). One G is the force required to accelerate an object at the acceleration due to gravity at Earth's surface, which is approximately 9.80 m/s². Therefore, an acceleration of 1.4g is 1.4 times that value, which is about 13.72 m/s².