![]() ![]() However, if the object is already in motion, or if this situation is viewed from a moving inertial reference frame, that body might appear to speed up, slow down, or change direction depending on the direction of the force and the directions that the object and reference frame are moving relative to each other. In the simplest case, a force applied to an object at rest causes it to accelerate in the direction of the force. Learn more about Newton’s second law in the context of space by clicking here, and be sure to check out NASA’s Newton in Space lesson for educators of grades 5-8 here.Newton's second law says that when a constant force acts on a massive body, it causes it to accelerate, i.e., to change its velocity, at a constant rate. It’s thanks to Newton’s principles like his second law of motion that rocketeers were able to develop mighty space-age rockets like the Saturn V, which weighed 6.2 million pounds fully fueled on the launchpad and could generate 7.6 million pounds of thrust at liftoff. Newton’s second law gives them a way to do this.Īs NASA covers in their Rocket Principles lesson, the higher a rocket’s propellant mass, the faster the gas in the rocket’s chamber can escape, generating a greater amount of thrust at launch. In short, rocket scientists must consider all of a rocket’s components (which make up its mass) to calculate the amount of force required to accelerate the rocket into space (must reach escape velocity, a speed of over 25,014 mph). This is why a rocket lifts off slowly at first, then speeds up. So, in keeping with Newton’s second law of motion, the rocket’s acceleration increases as its mass decreases. Thus, the rocket’s mass becomes smaller as the rocket ascends. The engines burn the propellant to fuel the rocket, using it all up until it is gone. During launch, a controlled explosion occurs, and gas is vented from the opening in the chamber, generating thrust and propelling the rocket in the opposite direction of the escaping gas- up to space.īut as a rocket lifts off, something happens to its mass. Simply put, a rocket is essentially a large chamber that holds gas under pressure with a small opening to vent the gas at liftoff. However, the largest part of a rocket’s mass goes to the solid and/or liquid propellant. It might not be the first thing you think about while watching a rocket blast off, but these spectacular events make for a great teachable moment in physics.Ī rocket’s mass is comprised of many different components – engines, payload, propellants, and more. Have you ever watched a rocket launch and wondered how such a massive object can lift off the Earth and into space? Would you have guessed that Newton’s second law of motion can help explain exactly what we see during launch? The above equation, F=ma, assumes a constant mass.įor objects that do not have a constant mass, the differential form of the equation is used, where the force is equivalent to an object’s change in momentum over time, or F=(m1V1-m0V0)/(t1-t0). Watch the STEMonstration clip below to watch NASA astronaut Randy Bresnik demonstrate Newton’s second law of motion onboard the International Space Station (ISS):īut what if an object’s mass isn’t constant? Well, that’s where things get interesting. Lastly, the mass of an object is the amount of matter that an object contains, and unlike weight, this quantity will not change with location. Acceleration can be defined as an object’s change in velocity over time, considering both speed and direction. However, it might help to first define these terms.Ī force is simply a push or pull acting upon an object. ![]() To put things simply, an object’s acceleration is dependent upon the amount of force that is applied to it, and its mass. Newton’s second law can be summed up in a simple mathematical equation where Force (F) is equivalent to the mass of an object (m) multiplied by its acceleration (a), or F=ma. Today, we are taking a closer look at Newton’s second law and how it can be applied to human spaceflight. Each month, in our new Science in Action series we uncover the science behind spaceflight.Ĭhances are, you’ve heard of Newton’s three laws of motion.
0 Comments
Leave a Reply. |