Pls someone help with number 3

Physics

1 answer:

mars1129 [50]3 years ago

7 0

Rocket thrust equation
= ( mass flow rate of fuel burnt ) X (Velocity of gas ejected ) + ( Exit Pressure - Outdoor Pressure ) X ( Area of exhaust )

In this case, we can assume the exit pressure = outdoor pressure and since area of exhaust is not given, it can be assumed to be negligible.

In this case, by Newton 3rd’s law,

Force exerted by gas on rocket
= Force exerted by rocket on gas
= (10kg/s) X (5 x 10^3 m/s)
= 5 x 10^4 N

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A railroad car moves under a grain elevator at a constant speed of 3.20 m/s. Grain drops into the car at the rate of 240 kg/min.

dedylja [7]

Answer:

F = 768 N

Explanation:

It is given that,

Speed of the elevator, v = 3.2 m/s

Grain drops into the car at the rate of 240 kg/min, $\dfrac{dm}{dt}=240\ kg/min = 4\ kg/s$

We need to find the magnitude of force needed to keep the car moving constant speed. The relation between the momentum and the force is given by :

$F=\dfrac{dp}{dt}$

$F=m\dfrac{dv}{dt}+v\dfrac{dm}{dt}$

Since, the speed is constant,

$F=m\dfrac{dv}{dt}$

$F=v\dfrac{dm}{dt}$

$F=3.2\times 240$

F = 768 N

So, the magnitude of force need to keep the car is 768 N. Hence, this is the required solution.

5 0

3 years ago

Doug is doing work. Without knowing exactly what he is doing, which can be said about the work he is doing?

WARRIOR [948]

<h3>Answer;</h3>

<em>Energy is transferred.</em>

<h3>Explanation;</h3>

Work is the force applied over a given distance, in other words work is the product of force and distance. That is; Work = force × distance.
Work is measured in Joules.

Energy on the other hand, is the ability to do work.

According to the principle of work-energy a change in the kinetic energy is equivalent to the net work don e by the object. Therefore, when work is being done energy is being transferred from one point to another.

8 0

3 years ago

Read 2 more answers

A man does 4,780 J of work in the process of pushing his 2.70 103 kg truck from rest to a speed of v, over a distance of 25.5 m.

wolverine [178]

Answer:

(A) Velocity will be 1.88 m/sec

(b) Force will be 187.45 N

Explanation:

We have given work done = 4780 j

Distance d = 25.5 m

(A) Mass of the truck m = $m=2.70\times 10^3kg$