Final answer:
The question relates to calculating acceleration using kinematic equations and Newton's second law of motion. Option a is correct for a body accelerating from rest, and option c correctly applies Newton's second law to determine a body's acceleration.
Step-by-step explanation:
When solving problems involving force and acceleration, it's important to use the correct equations. For example, the problem where a body starts from rest and accelerates at 4 m/s² for 2 seconds: we can use the kinematic equation v = u + at, where v is final velocity, u is initial velocity (0 since it starts from rest), a is acceleration and t is time. Therefore, v = 0 + (4 m/s² * 2 s) = 8 m/s, which means option a is correct.
In another scenario, if we know the mass of a body and the force applied to it, we can calculate acceleration using Newton's second law of motion, which states that F = ma (force equals mass times acceleration). If a force of 4 N is applied to a 2 kg mass, then a = F/m, or a = 4 N / 2 kg = 2 m/s², which confirms that option c is correct. These examples illustrate how to use foundational physics concepts to determine acceleration and related quantities.