Question

Rank each satellite based on the net force acting on it. Rank from largest to smallest.

• 1. m= 100kg, L = 2500m, v= 160 m/s
• 2. m= 300kg L = 10000m, v= 80 m/s
• 3. m = 400kg L = 2500m, v= 80 m/s
• 4. m = 200kg L = 5000m, v= 160 m/s
• 5. m = 800kg L = 10000m, v= 40 m/s
• 6. m = 200kg L = 5000m, v= 120 m/s

Answer 1

Concepts and reason

The required concept to solve the problem is the centripetal force. First, find the net force acting on each of the satellites. Then, rank the satellite from largest to smallest based on the net force acting on it.

Fundamentals

A satellite's motion is a projectile motion. The only force acting on the satellite is gravity. As the satellite moves in a circular motion, the force acting on the satellite is the centripetal force. This centripetal force is provided by gravity. Centripetal force is given by \(F_{C}=\frac{m v^{2}}{r}\)

Here, \(m\) is the mass of the satellite, \(v\) is the velocity of the satellite, and \(r\) is the radius of the circular orbit. As the motion of the satellite is circular, the particle's velocity will be directed tangent to the circle at every point along the path. The acceleration is directed towards the center of the circle.

The only force acting on a satellite is the centripetal force provided by gravity. So,

$$ F_{n e t}=F_{C} $$

\(=\frac{m v^{2}}{L}\)

Here, \(m\) is the mass of the satellite, \(v\) is the velocity of the satellite and \(L\) is the radius of the circular orbit. For the first satellite:

\(F_{1}=\frac{m_{1} v_{1}^{2}}{L 1}\)

Substitute 100 kgform \(_{1}, 160 \mathrm{~m} /\) sfor \(v_{1}\) and 2500 mfor \(L_{1}\) in the above expression.

\(F_{1}=\frac{(100 \mathrm{~kg})(160 \mathrm{~m} / \mathrm{s})^{2}}{2500 \mathrm{~m}}\)

$$ =1024 \mathrm{~N} $$

For the second satellite:

\(F_{2}=\frac{m 2 v_{2}^{2}}{L_{2}}\)

Substitute 300 kgform \(_{2}, 80 \mathrm{~m} /\) sfor \(v_{2}\) and 10000 mfor \(L_{2}\) in the above expression.

\(F_{2}=\frac{(300 \mathrm{~kg})(80 \mathrm{~m} / \mathrm{s})^{2}}{10000 \mathrm{~m}}\)

\(=192 \mathrm{~N}\)

For the third satellite:

\(F_{3}=\frac{m_{3} v_{3}^{2}}{L_{3}}\)

Substitute 400 kgform \(_{3}, 80 \mathrm{~m} /\) sfor \(v_{3}\) and 2500 mfor \(L_{3}\) in the above expression.

\(F_{3}=\frac{(400 \mathrm{~kg})(80 \mathrm{~m} / \mathrm{s})^{2}}{2500 \mathrm{~m}}\)

$$ =1024 \mathrm{~N} $$

For the fourth satellite:

\(F_{4}=\frac{m_{4} v_{4}^{2}}{L_{4}}\)

Substitute 200 kgform \(_{4}, 160 \mathrm{~m} /\) sfor \(v_{4}\) and 5000 mfor \(L_{4}\) in the above expression.

\(F_{4}=\frac{(200 \mathrm{~kg})(160 \mathrm{~m} / \mathrm{s})^{2}}{5000 \mathrm{~m}}\)

\(=1024 \mathrm{~N}\)

For the fifth satellite:

\(F_{5}=\frac{m 5 v_{5}^{2}}{L_{5}}\)

Substitute 800 kgform \(_{5}, 40 \mathrm{~m} /\) sfor \(v_{5}\) and 10000 mfor \(L_{5}\) in the above expression.

\(F_{5}=\frac{(800 \mathrm{~kg})(40 \mathrm{~m} / \mathrm{s})^{2}}{10000 \mathrm{~m}}\)

\(=128 \mathrm{~N}\)

For the sixth satellite:

$$ F_{6}=\frac{m_{6} v_{6}^{2}}{L 6} $$

Substitute \(200 \mathrm{~kg}\) for \(m_{6}, 120 \mathrm{~m} / \mathrm{s}\) for \(v_{6}\) and \(5000 \mathrm{~m}\) for \(L_{6}\) in the above expression.

$$ \begin{array}{c} F_{6}=\frac{(200 \mathrm{~kg})(120 \mathrm{~m} / \mathrm{s})^{2}}{5000 \mathrm{~m}} \\ =576 \mathrm{~N} \end{array} $$

The only force acting on a satellite is the centripetal force which is the ratio of the product of mass of the satellite and the square of the velocity to the radius of the satellite's orbit.

From the calculated centripetal forces, it is clear that the satellites 1,3 and 4 have the same amount of force acting on it, which is the largest force. The satellite 6 has force acting on it which is the second largest. Satellite 2 has a slightly lower value of force than that of satellite 6 and satellite 5 which has the least amount of force acting on it. Hence, the ranking of the satellites from largest to smallest, based on the force acting on them is \(1=3=4>6>2>5\)

The ranking of the satellites from largest to smallest, based on the force acting on them, is \(1=3=4>6>2>5\)

As the only force acting on a projectile is gravity, a satellite has an only gravitational force acting on it. The motion of the satellite around a planet is circular. So, there is the centripetal force acting on it. This centripetal force is provided by gravity. Thus, the net force acting on a satellite depends on the satellite's mass, the velocity with which it rotates around the planet, and the radius of the circular orbit followed by the satellite.

The ranking of the satellites from largest to smallest, based on the force acting on them is \(1=3=4>6>2>5\)