Net force and position of objects in space

In summary, the conversation is about the incorrect answers obtained when using the equation Fnet = Gm1m2/d^2 <unit vector> to calculate the force between two objects. The person suggests using the steps of finding the net force and then dividing it by the mass and multiplying it by the time interval, but this also gives an incorrect answer. Another approach of subtracting the vector of the planet by the star and using Gm1m2/d^2 times the unit vector is also mentioned, but this also leads to a wrong answer. The person advises against giving numerical answers and suggests estimating the answer before using a calculator.
  • #1
dayspassingby
2
0
Homework Statement
Q1) t = 493 s after midnight, a spacecraft of mass 2800 kg is located at position <9 × 105, 8 × 105, -3 × 105> m, and at that time an asteroid whose mass is 9 × 1015 kg is located at position <6 × 105, -9 × 105, -14 × 105 > m. There are no other objects nearby.

a) Calculate the (vector) force acting on the spacecraft.

b) At 493 s the spacecraft's momentum was , and at the later time 500 s its momentum was . Calculate the (vector) change of momentum .

Q2) A star of mass 3 × 1030 kg is located at <8 × 1012, 5 × 1012, 0> m. A planet of mass 6 × 1024 kg is located at <4 × 1012, 9 × 1012, 0> m and is moving with a velocity of <0.6 × 104, 1.1 × 104, 0> m/s.

a) During a time interval of 1 × 106 seconds, what is the change in the planet's velocity?\

b) During this time interval of 1 × 106 seconds, what is the change in the planet's position?

Q3) A planet of mass 7 × 1024 kg is at location <-2 × 1011, 5 × 1011, 0> m. A star of mass 4 × 1030 kg is at location <2 × 1011, -2 × 1011, 0> m. What is the force exerted on the planet by the star? (It will probably be helpful to draw a diagram, including the relevant vectors.)
Relevant Equations
Fnet = Gm1m2 / d^2 *unit vector
Q1a)
- My current wrong answer is <-5.9e7, -3.3e8, -2.17e8> I used the Fnet = Gm1m2 / d^2 <unit vector> But i keep getting a dif answer each time

Q2a) - I thought i could find net force and then divide it by the mass, and multiply it by the time interval. However I got the answer <-4.5, 4.5, 0> which is wrong

Q3)
I subtracted the planet by the star vector. Then, I used Gm1m2 / d^2 times the unit vector. But that just gave me <-1.43e21, 2.495e21, 0> Which is wrong
 
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  • #2
It is preferred that you post each problem as a separate thread.

In each case, please post all your working.
In 2a, will the force be sufficiently constant over that period to treat it as such?
 
  • #3
Hello @dayspassingby

:welcome: ##\qquad## !​

Please don't give the numerical answers you get but post the steps you take to get them.
And have pity on us: you don't mean 9135 kg when you write 9 x 1015 kg. So write 9 x 1015 kg using the superscript button
1643417337585.png

or learn a little ##\TeX## with the
1643417399237.png
to get ##9\times 10^{15} ## kg

https://www.physicsforums.com/threads/homework-help-guidelines-for-students-and-helpers.686781/

dayspassingby said:
keep getting a dif answer each time
Tip: estimate the answer (coarsely) before using a calculator. In this case, do you really expect forces to the tune of ##10^8## N ? ##\ ##
 
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FAQ: Net force and position of objects in space

1. What is net force and how is it related to the position of objects in space?

Net force is the overall force acting on an object, taking into account all the individual forces acting on it. The net force determines the acceleration of an object according to Newton's second law of motion. The position of an object in space is affected by the net force acting on it, as the net force causes a change in the object's velocity and therefore its position.

2. How does the net force affect the motion of objects in space?

The net force acting on an object determines its acceleration, which in turn affects its motion. If the net force is zero, the object will maintain its current state of motion (either at rest or moving at a constant velocity). If the net force is not zero, the object will experience a change in velocity, causing it to accelerate or decelerate.

3. What is the relationship between net force and gravitational force in space?

In space, the only significant force acting on objects is gravitational force. The net force acting on an object in space is equal to the gravitational force acting on it. This is because there are no other forces (such as friction or air resistance) to counteract the gravitational force.

4. Can the net force on an object in space ever be zero?

Yes, the net force on an object in space can be zero if all the individual forces acting on it cancel each other out. This can happen when the object is in a state of equilibrium, where it is either at rest or moving at a constant velocity.

5. How does the position of objects in space affect the net force acting on them?

The position of objects in space does not directly affect the net force acting on them. However, the position of objects can affect the individual forces acting on them, which in turn can affect the net force. For example, the gravitational force acting on an object will change depending on its distance from other objects with mass.

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