How does the energy used by a 100 W lightbulb compare with the energy used by a 40 W lightbulb in a given amount of time? The 10
2 answers:
The correct answer is
<span>The 100 W bulb uses 2.5 times more energy
In fact, the power is the amount of energy used per unit of time. This means that the light bulb of 100 W uses 100 J in one second, and the light bulb of 40 W uses 40 J in one second, and if we compare the two numbers, we get
</span>
<span>so, the 100 W light bulb uses 2.5 times more energy than the 40 W light bulb.</span>
<span>The 100 W bulb uses 2.5 times more energy
In fact, the power is the amount of energy used per unit of time. This means that the light bulb of 100 W uses 100 J in one second, and the light bulb of 40 W uses 40 J in one second, and if we compare the two numbers, we get
</span>
<span>so, the 100 W light bulb uses 2.5 times more energy than the 40 W light bulb.</span>
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Answer:
Approximately .
Explanation:
This question suggests that the rotation of this object slows down "uniformly". Therefore, the angular acceleration of this object should be constant and smaller than zero.
This question does not provide any information about the time required for the rotation of this object to come to a stop. In linear motions with a constant acceleration, there's an SUVAT equation that does not involve time:
,
where
is the final velocity of the moving object,
is the initial velocity of the moving object,
is the (linear) acceleration of the moving object, and
is the (linear) displacement of the object while its velocity changed from
The angular analogue of that equation will be:
, where
and
are the initial and final angular velocity of the rotating object,
is the angular acceleration of the moving object, and
is the angular displacement of the object while its angular velocity changed from
For this object:
, whereas
.
The question is asking for an angular acceleration with the unit . However, the angular displacement from the question is described with the number of revolutions. Convert that to radians:
.
Rearrange the equation and solve for
:
.