<span>Recall formula for Kinetic energy is:
KE = 1/2mv^2, where KE = 275J
and momentum (which is 25.0 kg m/s) = m*v
Therefore substitute for KE and mv in the equation above to get speed
=> 275 = 0.5 * 25 * v
v = 275/12.5
v = 22m/s
to get mass m, recall momentum = m*v
=> 25= 22*m
m= 25/22 = 1.3663kg</span>
Answer:
The area of the portion of the windshield cleaned by the 7-in wiper blade is 62.49 in²
Explanation:
Given
Length of blade = 9 inches
Angle of rotation = 93°
We're to calculate the area of the portion of the windshield cleaned by the 7-in wiper blade?
We'll solve this by using area of a sector.
Area of a sector = ½r²θ
where θ is in radians.
So, angle of rotation (93°) must first be converted to radians
Converting 93º to radians, we get 31π/60
The area of the region swept out by the wiper blade = (area of the sector where r = 9 and
θ = 31π/60) - (area of the sector where r = (9-7) and θ = 31π/60).
We're making use of 9-7 because that region is outside the boundary of the 7in blade
So Area = ½*9²*31π/60 - ½*2²*31π/60
Area = ½*31π/60(9²-7²)
Area = 31π/120 * (81 - 49)
Area = 31π/120 * 32
Area = 992π/120
Area = 62.49151386765697 in²
Area ≈ 62.49 in²
Hence, the area of the portion of the windshield cleaned by the 7-in wiper blade is 62.49 in²
Actually, they're not. There's a group of stars and constellations arranged
around the pole of the sky that's visible at any time of any dark, clear night,
all year around. And any star or constellation in the rest of the sky is visible
for roughly 11 out of every 12 months ... at SOME time of the night.
Constellations appear to change drastically from one season to the next,
and even from one month to the next, only if you do your stargazing around
the same time every night.
Why does the night sky change at various times of the year ? Here's how to
think about it:
The Earth spins once a day. You spin along with the Earth, and your clock is
built to follow the sun . "Noon" is the time when the sun is directly over your
head, and "Midnight" is the time when the sun is directly beneath your feet.
Let's say that you go out and look at the stars tonight at midnight, when you're
facing directly away from the sun.
In 6 months from now, when you and the Earth are halfway around on the other
side of the sun, where are those same stars ? Now they're straight in the
direction of the sun. So they're directly overhead at Noon, not at Midnight.
THAT's why stars and constellations appear to be in a different part of the sky,
at the same time of night on different dates.
As an egg falls towards the floor, it begins to travel faster and faster. When it slams into the floor, the egg is stopped almost immediately. This force of the floor against the eggshell is too large, so it breaks.
