Final answer:
The force needed to accelerate a 5-kg object at 20 m/s² is 100 N, following Newton's Second Law of Motion. Increasing applied force results in increased acceleration, and normal reaction acts perpendicular to the surface, not in the direction of gravity. An external force is required to move a stationary object in outer space. Therefore, the correct option is B.
Step-by-step explanation:
Newton's Second Law of Motion
To determine the force required to accelerate a 5-kg object at 20 m/s², we use Newton's Second Law of Motion, which states that the force (F) applied on an object is equal to the mass (m) of the object multiplied by the acceleration (a) of the object (F = m * a). Applying this formula, the force needed is 5 kg * 20 m/s² = 100 N. Therefore, answer a is incorrect, and the correct answer should be 100 N. If an applied force is increased by 1 N, the acceleration increases accordingly, assuming the mass remains constant. This concept is part of the fundamental principles of physics related to force and motion, and it is typically covered in high school physics courses. The given statement regarding normal reaction is false; normal reaction is a support force that acts perpendicular to the surface an object is resting on and opposes the force of gravity to some extent, but it does not act in the direction of the force of gravity.
For a stationary object in outer space away from gravitational influence, it is true that an external force is required to set the object in motion, according to Newton's First Law of Motion or the law of inertia.