The time required by the car to stop is 4.916 sec.
Since the car is moving with the constant deceleration we can apply the first equation of motion to calculate the time required by the car to stop.
The first equation of motion is given as
V=u+at
Here, V=final speed of the car=0 mi/h as the car stops
u =initial speed of the car=55 mi/hr=24.58 m/s
a= acceleartion =-5 m/s^2 (here negative sign indicates for deceleration)
Now applying the values in the first equation
V=u+at
0=24.58-5*t
t=4.916 sec
Therefore the car will stops in 4.916 sec.
Take the moment car A starts to accelerate to be the origin. Then car A has position at time <em>t</em>
<em>x</em> = (20.0 m/s) <em>t</em> + 1/2 (2.10 m/s²) <em>t</em>²
and car B's position is given by
<em>x</em> = 300 m + (27.0 m/s) <em>t</em>
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Car A overtakes car B at the moment their positions are equal:
(20.0 m/s) <em>t</em> + 1/2 (2.10 m/s²) <em>t</em>² = 300 m + (27.0 m/s) <em>t</em>
300 m + (7.00 m/s) <em>t</em> - (1.05 m/s²) <em>t</em>² = 0
==> <em>t</em> ≈ 20.6 s
Answer:
Current needed = 704A
Explanation:
Using the fomula; torque(τ) = (I)(A)(B)Sinθ
Where B = uniform magnetic field
I = current and A = Area
Diameter = 19cm = 0.19m so, radius = 0.19/2 = 0.095m
Area(A) = πr^(2) = πr^(2)
= π(0.095)^(2) = 0.0284 m^(2)
Now, B(earth)= 5x10^-5 T
While, we can ignore the angle because it's insignificant since the angle of the wire is oriented for maximum torque in the earth's field.
Now, if we arrange the formula to solve for charge (I):
I = (τ)/(A)(B)
I = (1.0x10^-3) / (0.0284)(5x10^-5)
I = 704A
Choice D). is on the right track, but it's stated incorrectly.
The wavelengths of light coming from a galaxy that's moving toward us <em>are </em>
<em>shorter</em> than they were when they left the galaxy. When we see them, they're
shorter than they should be.
(This is called a "blue shift" in the spectrum of the galaxy, because blue is the
short-wavelength end of the spectrum of visible light. If the wavelength of some
light somehow becomes shorter, then the color of the light changes toward the
direction of blue.)
If the source of light is moving toward us, then the wavelength we see is shorter
than it should be. If the source is moving away from us, then the wavelength
we see is longer than it should be. The whole trick to this is knowing <u>what</u> the
wavelength of the light we see <em>should be</em> !
