Launch to Powered ascent – what is
happening to the rocket? Is its motion changing? How is it changing? Which and how do the laws explain this motion? How is thrust generated? Which law and how does it explain thrust?
Newton's first law is an object in motion and will stay in motion, and an object at rest will stay at rest until acted on by an unbalanced force. Before the launch, the rocket is at rest. Demonstrating Newton’s third law, every action has an equal and opposite reaction. The weight of the rocket is balanced by the reaction of the earth to the weight. When the rocket is launched, Weight and Thrust act upon each other until the thrust becomes greater than the weight, and the net force is positive upward. The rocket then accelerates upward and the velocity increases. Exhibiting Newton’s third law, the exhaust flow is pushed backward, and the engine is pushed forward as a reaction. More specifically, through the combustion of fuel, hot exhaust gas is produced and accelerates at the rear of the rocket. The reaction is the thrusting force on the engine mount.
Coasting flight – why does the rocket
continue to ascend? Which law and how does it explain this?
During the coasting flight Newton’s third law is in action. The force of weight and the thrust from the engine oppose each other equally, so the rocket continues to ascend. As the weight begins to increase, the forces are unbalanced and negative net force causes the rocket begins to move at a downward slope.
Slow Descent to Landing – what is happening to the rocket? What is responsible for this? Which law and how does it explain this motion?
During the slow descent and landing there is no longer the force of the thrust, so weight pulls the rocket downwards. Air resistance pushes up against the descending rocket but is only strong enough to slow it down a little bit. There is an unbalanced force and a negative net force that acts upon the rocket. Weight continues to act upon the rocket and the parachute opens up and causes more air resistance, slowing the rocket further until it finally reaches the ground.
Once the rocket has landed, it is at rest with no unbalanced forces act upon it. The weight of the rocket pushes down on the ground and the ground pushes back up against it with an equal and opposite force.
Powered ascent:
ReplyDeleteCorrect application of third law to how the engine generates thrust.
Coasting flight:
The third law is about how 2 objects interact, NOT two forces on the same object. It does not apply to coasting flight. In addition, there is no thrust during this phase. The rocket already has a positive velocity upward and will continue to move up (Newton's first law). It will slow due to an unbalanced force from gravity and drag (Newton's 2nd law).