Question

multiple select question
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which statements about equilibrium are accurate?
a skydiver descending at constant velocity under her parachute is in a state of equilibrium.
newtons first law identifies a net force as something that disturbs a state of equilibrium.
for a system to be in a state of equilibrium, there must be no forces exerted on it by the external world.
for a system to be in a state of equilibrium, it must have zero velocity and zero acceleration.
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Explanation:

• Option A: When a skydiver descends at a constant velocity, according to Newton's first law ($F = ma$, and $a = 0$ when $v$ is constant), the net force on the skydiver is zero. So, the skydiver is in equilibrium.
• Option B: Newton's first law states that an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an un - balanced force. So, a net force disturbs the state of equilibrium.
• Option C: For a system to be in equilibrium, the net force acting on it must be zero ($\sum F=0$), not that there are no forces. There can be multiple forces acting on the system as long as their vector sum is zero.
• Option D: For a system to be in equilibrium, the net force must be zero ($\sum F = 0$), which implies acceleration $a = 0$. But the velocity can be non - zero (constant velocity). For example, the skydiver in option A has non - zero velocity but is in equilibrium.

Answer:

A. A skydiver descending at constant velocity under her parachute is in a state of equilibrium.
B. Newton's first law identifies a net force as something that disturbs a state of equilibrium.