A force acting on a body causes a change in the momentum of the from 12 kgms-1 to 16 kgms-1 in 0.2 s. calculate the magnitude of
1 answer:
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1) Initial upward acceleration:
2) Mass of burned fuel:
Explanation:
1)
There are two forces acting on the rocket at the beginning:
- The force of gravity, of magnitude , in the downward direction, where
is the rocket's mass
is the acceleration of gravity
- The thrust of the motor, T, in the upward direction, of magnitude
According to Newton's second law of motion, the net force on the rocket must be equal to the product between its mass and its acceleration, so we can write:
(1)
where a is the acceleration of the rocket.
Solving for a, we find the initial acceleration:
2)
When the rocket reaches an altitude of 5000 m, its acceleration has increased to
The reason for this increase is that the mass of the rocket has decreased, because the rocket has burned some fuel.
We can therefore rewrite eq.(1) as
where
is the new mass of the rocket
Re-arranging the equation and solving for m', we find
And since the initial mass of the rocket was
This means that the mass of fuel burned is
In a circuit, the electromotive force can be said to be the "source" of the "pushed electrons". This push then creates what is known as a current, which is the flow of electric charge through the circuit. This flow can be slowed down or restricted by a resistor, and this is also what can be harnessed in order to use electric power.
Explanation:
The electromotive force is the potential difference produced by the battery in the circuit. When the circuit is connected to the battery, this potential difference causes the electron to start moving towards the point at higher potential: in this sense, the electromotive force is said to be the "source" of the "pushed electrons".
This flow of electrons moving in the circuit is known as current.
Then, in the circuit, it is possible to place a piece of circuit with a smaller cross-section that restricts the flow of electrons: this component is known as resistor, and its property of restricting the flow of electron is known as resistance.
In a circuit, electromotive force (V), current (I) and resistance (R) are related by Ohm's law:
Finally, when a current passes through a resistor, part of the electric energy is converted into thermal energy, and some power is dissipated through the resistor. The power dissipated is given by
This power can be harnessed, for instance, if the resistor is connected to a light bulb: the energy is transformed into heat and light, and so the light bulb turns on, providing illumination.
Learn more about current and resistance:
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