Which statement is true about alkali metals? A. Some of them explode when exposed to water. B. They are in group 18 of the perio
2 answers:
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Answer:
Approximately 0.0898 W/m².
Explanation:
The intensity of light measures the power that the light delivers per unit area.
The source in this question delivers a constant power of . If the source here is a point source, that
of power will be spread out evenly over a spherical surface that is centered at the point source. In this case, the radius of the surface will be 9.6 meters.
The surface area of a sphere of radius is equal to
. For the imaginary 9.6-meter sphere here, the surface area will be:
.
That power is spread out evenly over this 9.6-meter sphere. The power delivered per unit area will be:
.
1) The car overtakes the truck at a distance of 160 m far from the intersection.
2) The velocity of the car is 40 m/s
Explanation:
1)
The car is travelling with a constant acceleration starting from rest, so its position at time t (measured taking the intersection as the origin) is given by
where
is the acceleration
t is the time
On the other hand, the truck is travelling at a constant velocity, therefore its position at time t is given by
where
v = 20 m/s is the velocity of the truck
t is the time
The car overtakes the truck when the two positions are the same, so when
So, after a time of 8 seconds. Therefore, the distance covered by the car during this time is
So, the car overtakes the truck 160 m far from the intersection.
2)
The motion of the car is a uniformly accelerated motion, so the velocity of the car at time t is given by the suvat equation
where
v is the velocity at time t
u is the initial velocity
a is the acceleration
For the car in this problem, we have:
u = 0 (it starts from rest)
And we know that the car overtakes the truck when
t = 8 s
Substituting into the equation,
Learn more about accelerated motion:
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