in case a, an object is moving in a straight line at a constant speed of 9.8 m/s. in case b, an object is…
in case a, an object is moving in a straight line at a constant speed of 9.8 m/s. in case b, an object is moving in a straight line with a constant acceleration of 9.8 m/s². which of the following statements is true?\n\na nonzero net external force acts on the object in case a only.\n\na nonzero net external force acts on the object in both cases.\n\na nonzero net external force acts on the object in neither case.\n\na nonzero net external force acts on the object in case b only.
Answer
Explanation:
Step1: Recall Newton's second - law
Newton's second - law is $F = ma$, where $F$ is the net external force, $m$ is the mass of the object, and $a$ is the acceleration.
Step2: Analyze Case A
In Case A, the object is moving at a constant speed. So, the acceleration $a = 0$. According to $F=ma$, when $a = 0$, $F=0$ (assuming non - zero mass $m$).
Step3: Analyze Case B
In Case B, the object has a non - zero constant acceleration $a=9.8\ m/s^{2}$. Since $m\neq0$ and $a\neq0$, from $F = ma$, we have $F\neq0$.
Answer:
D. A nonzero net external force acts on the object in Case B only.