# Physics 11 Net force and Acceleration

• anOldMan
In summary, the conversation discusses a fully loaded Saturn rocket with a mass of 2.92x10^6kg and an engine thrust of 3.34x10^7N. The questions asked include the weight of the rocket, the net force on the rocket when it blasts off, the acceleration as it leaves the launch pad, its speed after 60 seconds, and the effect of decreasing mass on acceleration as the rocket moves away. The answers are 2.92x10^7N for the weight, 4.2x10^6N for the net force, 144m/s^2 for the acceleration, and 86.4m/s for the speed after 60 seconds. The mass decreases as
anOldMan

## Homework Statement

g=10m/s^2
A fully loaded Saturn rocket has a mass of 2.92x10^6kg. Its engines have a thrust of 3.34x10^7N.

a) How much does the rocket weigh. answer 2.92x10^7 N
b) What is the net force on the rocket when it blasts off? answer 4.2x10^6N
c) What is the acceleration as it leaves the launch pad? 144m/s^2
d) What is its speed after 60 seconds? answer 86.4m/s
e) As the rocket moves away, the engine thrust is constant but the mass decreases - why? What effect does this have on acceleration. answer Fuel is consumed; m decreases, a increases.

F=ma P.E. =mgh

## The Attempt at a Solution

I have no idea how the answer for b) becomes 4.2x10^6N
Any help would be appreciated.

Part c

Based on the question I got the mass as 2.92 and the thrust as 33.4. 33.4 to match the exponent for both numbers. The answer I got when F/m=a is 33.4kg by m/s^2/2.92Kg=11.4m/s^2m/s^2. This is obviously wrong. What am I doing wrong?

The answer for b) is found by using the equation F=ma. We know the mass of the rocket (2.92x10^6kg) and the acceleration (g=10m/s^2), so we can plug those values in to find the net force. The calculation is 2.92x10^6kg x 10m/s^2 = 2.92x10^7N. This is the weight of the rocket, which is equal to the net force when the rocket is at rest on the launch pad. However, when the engines are blasting off, there is an additional thrust force of 3.34x10^7N. Therefore, the net force on the rocket when it blasts off is the sum of the weight and thrust forces, which is 2.92x10^7N + 3.34x10^7N = 4.2x10^7N. This is the answer for b).

I hope this clarifies the calculation for you. Feel free to reach out if you have any further questions.

## 1. What is net force?

Net force is the overall force acting on an object, taking into account both magnitude and direction. It is the sum of all individual forces acting on the object.

## 2. How is net force calculated?

Net force is calculated by adding together all forces acting on an object in the same direction, and subtracting any forces acting in the opposite direction. The resulting number is the net force.

## 3. What is acceleration?

Acceleration is the rate of change of velocity over time. It can be thought of as the object's speed increasing or decreasing, or changing direction.

## 4. How is acceleration related to net force?

According to Newton's Second Law, acceleration is directly proportional to the net force acting on an object. This means that a greater net force will result in a greater acceleration, and vice versa.

## 5. What is the difference between net force and acceleration?

The main difference between net force and acceleration is that net force is a physical quantity that describes the overall force acting on an object, while acceleration is a measure of how the object's velocity is changing. Net force has both magnitude and direction, while acceleration only has magnitude.

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