A 125 kg including all the contents rocket has an engine...

A 125-kg (including all the contents) rocket has an engine that produces a constant vertical force (the thrust) of 1720 N. Inside this rocket, a 15.5-N electrical power supply rests on the floor. (a) Find the acceleration of the rocket. (b) When it has reached an altitude of 120 m, how hard does the floor push on the power supply? (Hint: Start with a free-body diagram for the power supply.)

Transcript

00:03 So for number 16, part a, there is a rocket that has force from the thrusters, making it go up, and weight due to gravity.

00:27 So the force is told to us that it is 1720 newtons.

00:34 Weight is equal to mass times gravity, with the mass being equal to 125 kilograms.

00:43 So the weight is equal to 125 kilograms times gravity, which is 9 .8 meters per second squared.

01:00 When you multiply that out, you will get 1 ,225 newons.

01:07 From there, we can find the sum of the forces.

01:13 So the sum of the forces will be equal to the force of the thrusters minus the weight because the force is upward while the weight is downward.

01:26 That is why the force is positive and the weight is negative.

01:31 So from there, we can change the sum of the forces into mass times acceleration because f equals m, a, right? so making this mass times acceleration is equal to the force of the thrusters minus the weight.

01:54 We want to find we know the mass, we know the force and we know the weight.

02:02 We want to find the acceleration.

02:04 So we will divide by mass on both sides so we can get acceleration by itself.

02:17 So that is equal to the force of the thrusters, which is 1720 newtons, minus 12, 25 newtons, which is the weight, all divided by the mass of the rocket, which is 125 kilograms.

02:37 And that turns out to be 3 .96 meters per second squared, or the accelerators.

02:51 The next part of this problem, part b, asked to find the force that the power supply, force that the floor is pushing on the power supply...

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