How does a rocket uses newtons laws of motion?

Answer 1

This law of motion is essentially a statement of a mathematical equation. The three parts of the equation are mass (m), acceleration (a), and force (f). Using letters to symbolize each part, the equation can be written as follows:

f = maBy using simple algebra, we can also write the eauation two other ways: a = f/mm = f/aThe first version of the equation is the one most commonly referred to when talking about Newton's second law. It reads: force equals mass times acceleration. To explain this law, we will use an old style cannon as an example.

When the cannon is fired, an explosion propels a cannon ball out the open end of the barrel. It flies a kilometer or two to its target. At the same time the cannon itself is pushed backward a meter or two. This is action and reaction at work (third law). The force acting on the cannon and the ball is the same. What happens to the cannon and the ball is determined by the second law. Look at the two equations below.

f = m(cannon) * a(cannon)f = m(ball) * a(ball)The first equation refers to the cannon and the second to the cannon ball. In the first equation, the mass is the cannon itself and the acceleration is the movement of the cannon. In the second equation the mass is the cannon ball and the acceleration is its movement. Because the force (exploding gun powder) is the same for the two equations, the equations can be combined and rewritten below. m(cannon) * a(cannon) = m(ball) * a(ball)In order to keep the two sides of the equations equal, the accelerations vary with mass. In other words, the cannon has a large mass and a small acceleration. The cannon ball has a small mass and a large acceleration.

Let's apply this principle to a rocket. Replace the mass of the cannon ball with the mass of the gases being ejected out of the rocket engine. Replace the mass of the cannon with the mass of the rocket moving in the other direction. Force is the pressure created by the controlled explosion taking place inside the rocket's engines. That pressure accelerates the gas one way and the rocket the other.

Some interesting things happen with rockets that don't happen with the cannon and ball in this example. With the cannon and cannon ball, the thrust lasts for just a moment. The thrust for the rocket continues as long as its engines are firing. Furthermore, the mass of the rocket changes during flight. Its mass is the sum of all its parts. Rocket parts includes engines, propellant tanks, payload, control system, and propellants. By far, the largest part of the rocket's mass is its propellants. But that amount constantly changes as the engines fire. That means that the rocket's mass gets smaller during flight. In order for the left side of our equation to remain in balance with the right side, acceleration of the rocket has to increase as its mass decreases. That is why a rocket starts off moving slowly and goes faster and faster as it climbs into space.

Newton's second law of motion is especiaily useful when designing efficient rockets. To enable a rocket to climb into low Earth orbit, it is necessary to achieve a speed, in excess of 28,000 km per hour. A speed of over 40,250 km per hour, called escape velocity, enables a rocket to leave Earth and travel out into deep space. Attaining space flight speeds requires the rocket engine to achieve the greatest action force possible in the shortest time. In other words, the engine must burn a large mass of fuel and push the resulting gas out of the engine as rapidly as possible.

Answer 2

The first Newton law states that an object at rest will stay at rest and an object that is moving with stay moving unless a forces acts on them. While the rocket is in flight with water/fire being forced out there is a force so the rocket must be accelerating. For the second Newton law the rocket is decreasing as it loses pressure. The acceleration may be changing but if the mass and force decreased at the same time to make it constant. The third law the rocket is going forwards as the water/fuel is pushed out backwards.

Answer 3

An object at rest tends to stay at rest and an object in constant motion tends to stay in motion unless acted upon by an unbalanced force

When a rocket is launched, an unbalanced force is being acted upon it. Before it was launched the force of the gravity pushing it down, and the ground beneath it was equal, or balanced. The unbalanced force was was the action of the fuel or such being shot from the bottom. More so, this would apply to Newton's third law.

Answer 4

All of them would apply. You must exert a force on the rocket to make it move (1st). This force is proportional to its mass and acceleration (2nd). The rocket must exert a force on the air, and so the air exerts a force back on the rocket to make it go up (3rd)

Answer 5

Sir Isaac newton observed that for every action there is an equal and opposite reaction. A rocket works like a squid- there's something that gets squirted out in one direction and the squid or rocket goes in the other direction.

But there's an interesting difference too. A squid squirts out a heavy (large mass) jet of water at a fairly low speed. A rocket squirts out a very light (small mass) jet of gas, at a very high speed.

Newton was building on Galileo's work on acceleration, and it was one of the two of them who observed that the energy in a system can be understood as 1/2 Mass X Velocity2. If I have a pound of water and I squirt it out at 10 feet per second, the energy is 10/2 * 10 * 10= 5 * 100 = 500 foot pounds per second. If I have 100 pounds of water and I squirt it at 1 foot per second, that's 100/2 * 1 * 1, or 50 (surprise!) foot pounds per second. (works the same in metric measurements too - about .5 Kg of water at about 3 M/sec vs about 5 Kg water at .3 M/sec:

.5/2 * 3 * 3 vs 5/2 * .3 * .3 = .25 * 9 or 2.25 vs 2.5 * .09 = .225... theres a 10 to one difference, the faster jet having the more energy.

So in a rocket, the very light weight gas goes blasting out one end of the rocket and because of its very high velocity, it pushes hard enough to lift the rocket.

Notice that the gas jet is pushing against the rest of the rocket. Its not pushing against the air, just as the squid isn't pushing against the water its in, the squid's jet is pushing against the squid. So a rocket works just fine in a vacuum, in space, and a squid out of water has one big chance to move by squirting...

Famously, when Dr. Robert Goddard was inventing the liquid fueled rocket, no less than the New York Times criticized him for proposing rocket flights in space, the editorial writer mistakenly believing a rocket pushes against the surrounding atmosphere.

Hope this helps. Extra points for who (Galileo? Newton?) noted that the precise measure of energy was 1/2 Mass * Velocity2. (one-half mass times velocity squared)

Answer 6

Newtons third law states that :

For every action there is an equal and opposite re-action.

Current rockets used on Earth use a liquid propellant which is forced out of the back of the rocket. As it escapes in one direction it creates a force in the opposite direction; in this case against the rocket itself forcing it in the opposite direction. Hopefully upward.

<---Action -----> Reaction

Answer 7

Every action (the fire pushing from the end of the rocket) has an equal and opposite reaction (the rocket moving)

Answer 8

Every action has an equal and opposite reaction.

The rocket expels gas out of the exhaust nozzle pushing down the rocket goes up.

Answer 9

the ground is exerting a force on the rocket causing it to take off