Applying Newtons laws (intro to physics problem)

In summary: The difference in mass will be the mass of the burned fuel.In summary, the rocket's initial upward acceleration is 15 m/s^2 and it has burned approximately 1333 kg of fuel at an altitude of 5.0 km.
  • #1
natty210
3
0
A 20000 rocket has a rocket motor that generates 3.0×105 of thrust.

What is the rocket's initial upward acceleration?
Express your answer using two significant figures.

At an altitude of 5.0 km the rocket's acceleration has increased to 6.0 m/s^2 . What mass of fuel has it burned?
Express your answer using two significant figures.
 
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  • #2
There are reasons for using units in physics, most notably that we know what kind of quantities we are talking about.

Let's assume 20000 is the mass in kilograms, and by 3.0×105 you mean 3.0×105 (rather than 315), and the corresponding unit is Newtons.

Then you are given the mass and upward force. What other forces act? What is the relation between force, mass and acceleration?

For the second question, let's assume that the thrust remains equal. So now the acceleration and force are given and you are asked for the mass. Again: what are the forces acting and what physical law do you know?

(By the way, when posting this question, you should have gotten a template in the posting form. May I be so bold as to inquire why you didn't use it?)
 
  • #3
natty210 said:
A 20000 rocket has a rocket motor that generates 3.0×105 of thrust.

What is the rocket's initial upward acceleration?
Express your answer using two significant figures.

At an altitude of 5.0 km the rocket's acceleration has increased to 6.0 m/s^2 . What mass of fuel has it burned?
Express your answer using two significant figures.

Thrust is the force. Use the basic equation [tex]F=ma[/tex] to find acceleration (don't forget the influence of gravity).

Since the thrust is assumed to be constant, then you can use that equation again to find the new mass of the rocket+fuel at the higher acceleration.
 

1. What are Newton's Laws of Motion?

Newton's Laws of Motion are three fundamental principles in physics that describe the behavior of objects in motion. They are: 1) The Law of Inertia, 2) The Law of Acceleration, and 3) The Law of Action and Reaction. These laws were developed by Sir Isaac Newton in the 17th century and are still used today to understand and predict the motion of objects.

2. How do these laws apply to real-world situations?

Newton's Laws of Motion can be applied to a wide range of real-world situations, from the movement of planets in our solar system to the motion of a car on a highway. These laws help us understand how objects move and how forces affect their motion. For example, the Law of Inertia explains why a moving car will continue to move forward even if the driver suddenly hits the brakes.

3. What is the first law of motion?

The first law of motion, also known as the Law of Inertia, states that an object at rest will remain at rest and an object in motion will continue in a straight line at a constant speed unless acted upon by an external force. This means that objects will not change their state of motion unless a force is applied to them.

4. How do we calculate acceleration using Newton's second law?

Newton's second law states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. This can be written as the equation F=ma, where F is the net force, m is the mass of the object, and a is the acceleration. This means that the greater the force applied to an object, the greater its acceleration will be.

5. Can Newton's laws be applied to objects in space?

Yes, Newton's laws of motion can be applied to objects in space. In fact, these laws were first developed to explain the motion of planets and other celestial bodies. The Law of Gravitation, which states that the force of attraction between two objects is directly proportional to their masses and inversely proportional to the square of the distance between them, is a direct result of Newton's laws and is crucial in understanding the motion of objects in space.

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