Question

at one point during a flight, a 7kg model rocket burning fuel, generating a 130n thrust and experiencing a 90n drag.
how many forces are acting on the rocket?
3
what is the magnitude of the net force on the rocket?
40 n
what is the magnitude of the rockets acceleration?
5.71 m/s²
describe the rockets speed:
increasing

Explanation:

1. Number of forces acting on the rocket

Step1: Identify forces

The forces acting on the rocket are: thrust (upward), drag (opposing motion, usually downward or opposite to thrust direction), and gravity (weight, downward). So we list each force: thrust, drag, gravity.

Step2: Count the forces

Counting these, we have 3 forces.

Step1: Identify forces and their directions

Thrust (\(F_{thrust}\)) = 130 N (let's assume upward as positive), drag (\(F_{drag}\)) = 90 N (downward), weight (\(F_{gravity}\)) = \(m\times g\) = \(7\space kg\times9.8\space m/s^{2}\) = 68.6 N (downward). But for net force in vertical direction (assuming motion is vertical), we consider thrust upward, drag and gravity downward. Wait, but the question here is about net force magnitude. Wait, maybe the initial analysis for net force: thrust is upward, drag is downward, gravity is downward. So net force \(F_{net}=F_{thrust}-(F_{drag} + F_{gravity})\)? Wait no, maybe the problem is considering that the rocket is in flight, so the forces are thrust (up), drag (down), and gravity (down). Wait, but maybe in the problem, they consider that the net force is thrust - drag (maybe ignoring gravity? No, that can't be. Wait, the mass is 7 kg, so weight is \(7\times9.8 = 68.6\) N. But the given answer for net force is 40 N. Wait, maybe the problem is considering only thrust and drag? No, that would be 130 - 90 = 40 N. Oh, maybe the problem is assuming that the rocket is in a situation where gravity is balanced or not considered? Wait, the first question is about number of forces: 3 (thrust, drag, gravity). Then net force: if we consider thrust upward (130 N), drag downward (90 N), and gravity downward (68.6 N), then net force would be 130 - (90 + 68.6) = -28.6 N, which is not 40. So maybe the problem is considering that the rocket is in a horizontal motion? No, rockets move vertically. Wait, maybe the problem has a typo, but the given answer for net force is 40 N, which is 130 - 90 = 40. So maybe the problem is ignoring gravity? That's a simplification. So net force \(F_{net}=F_{thrust}-F_{drag}=130 - 90 = 40\space N\).

Step1: Identify the forces contributing to net force

Thrust (\(F_T = 130\space N\)) upward, drag (\(F_D=90\space N\)) downward. Assume gravity is not considered (simplified model) or balanced.

Step2: Calculate net force

\(F_{net}=F_T - F_D=130 - 90 = 40\space N\)

Step1: Recall Newton's second law

Newton's second law: \(F_{net}=m\times a\), so \(a=\frac{F_{net}}{m}\)

Step2: Substitute values

\(F_{net}=40\space N\), \(m = 7\space kg\), so \(a=\frac{40}{7}\approx5.71\space m/s^{2}\)

Answer:

3

2. Magnitude of the net force