Question

short constructed response - read the question carefully. then enter your answer in the box provided.

1. explain how two of newton’s laws of motion occur simultaneously during a rocket launch.

Explanation:

1. Newton's First Law (Inertia): Before launch, the rocket is at rest (balanced forces: gravity and normal force from the launch pad). To start moving, an unbalanced force (thrust from engines) must act, overcoming inertia. During launch, if thrust equaled gravity, it would stay at constant velocity (but thrust exceeds gravity, so it accelerates).
2. Newton's Third Law (Action - Reaction): The rocket engines expel hot gases downward (action force). In response, the gases exert an equal - and - opposite upward force on the rocket (reaction force, thrust), propelling it upward.
3. Newton's Second Law ($F = ma$): The thrust ($F$) from the engines, minus the weight of the rocket ($mg$), creates a net force. As fuel burns, the rocket’s mass ($m$) decreases, and with a relatively constant thrust, the acceleration ($a=\frac{F_{net}}{m}$) increases, causing the rocket to speed up rapidly. (Choose two, e.g., Third and Second: Third provides the thrust force, Second explains how that force (along with gravity) causes acceleration as mass changes.)

Answer:

To explain two of Newton’s laws during a rocket launch:

Newton’s Third Law (Action - Reaction)

The rocket’s engines exert a downward force on the expelled hot gases (action). In return, the gases exert an equal - magnitude, upward - directed force (reaction, called thrust) on the rocket. This thrust is what lifts the rocket off the launch pad.

Newton’s Second Law ($\boldsymbol{F = ma}$)

The net force on the rocket is the thrust (upward) minus the rocket’s weight (downward, $F_{net}=F_{thrust}-mg$). As the rocket burns fuel, its mass ($m$) decreases. From $a=\frac{F_{net}}{m}$, with $F_{net}$ relatively constant (or increasing) and $m$ decreasing, the rocket’s acceleration ($a$) increases. This causes the rocket to speed up rapidly as it ascends.

(Alternatively, pair Third Law with First Law: Before launch, inertia (First Law) keeps the rocket at rest until thrust (from Third Law’s reaction) provides an unbalanced force to overcome inertia and start motion.)