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alisha [4.7K]
3 years ago
7

As a car heads down a highway traveling at a speed v away from a ground observer, which of the following statements are true abo

ut the measured speed of the light beam from the car's headlights? (Select all that apply.)
a. The ground observer measures the light speed to be c.
b. The driver measures the light speed to be c.
c. The driver measures the light speed to be c − v.
d. The ground observer measures the light speed to be c + v.
e. The ground observer measures the light speed to be c − v.
Physics
1 answer:
aliina [53]3 years ago
5 0

Answer:

a and b

Explanation:

According to theory of relativity by great Scientist Albert Eintein the speed of light is independent of frame of reference that the speed of light shall remain constnat whether the frame is inertial or non-inertial.

Therefore, both the ground observer and the driver shall measure same speed of light that is C.

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A scientist measures the number of flies in a room over time. The results are
snow_lady [41]
A. The number of files was constant.
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3 years ago
A man stands on a scale and holds a heavy object in his hands. What happens to the scale reading if the man quickly lifts the ob
Novosadov [1.4K]

Answer:

Explanation:

When he accelerates the heavy object up , the reading increases because an extra downward normal force acts on it, then scale reading returns to the same reading as when standing stationary, and then decreases as although he is lifting the heavy object , the acceleration is decreasing ,so the extra upward normal force acts.

6 0
3 years ago
A 5.0 kg cannonball is fired horizontally at 68 m/s from a 15-m-high cliff. A strong tailwind exerts a constant 12 N horizontal
jeka57 [31]

Answer:

3.7 m

Explanation:

ASSUMING this means extra distance beyond where the cannonball would land WITHOUT the wind assistance but in general ignoring air resistance. Hmmmmmm...tricky

The ball drops from vertical rest to ASSUMED horizontal ground 15 m below in a time of

t = √ (2h/g) = √(2(15)/9.8) = 1.75 s

Without the tail wind, the ball travels horizontally

d = vt = 68(1.75) = 119 m

The tailwind exerts a constant acceleration on the ball of

a = F/m = 12/5.0 = 2.4 m/s²

The average horizontal velocity during the flight is

v(avg) = (68 + (68 + 2.4(1.75)) / 2 = 70.1 m/s

so the distance with tailwind is

d = v(avg)t = 70.1(1.75) = 122.675 m

The extra distance is 122.675 - 119 = 3.675 = 3.7 m

8 0
3 years ago
Compare and contrast speed and velocity
Alex73 [517]
Where speed is distance/time, velocity is displacement/time. 

What this means is that velocity is the length covered in relation to the starting point. 
Speed is just the distance travelled no matter where you began. 

When going around a circular track, you might have a speed value. However, since you get back to the same location at every lap, you have 0 velocity. 

Hope I helped :)
8 0
3 years ago
A skier is pulled by a towrope up a frictionless ski slope that makes an angle of 12 degrees with the horizontal. The rope moves
MArishka [77]

Answer:

Explanation:

Given,

  • Work done by the rope 900 m/s.
  • Angle of inclination of the slope = \theta\ =\ 12^o
  • Initial speed of the skier = v = 1.0 m/s
  • Length of the inclined surface = d = 8.0 m

part (a)

The rope is doing the work against the gravity on the skier to uplift up to the inclined surface. Therefore the work done by the rope is equal to the work done on the skier due to the gravity

\therefore W_r\ =\ W_g\ =\ 900\ J

In both cases the height attained by the skier is equal. and the work done by gravity does not depend upon the speed of the skier.

part (b)

  • Initial speed of the skier = v = 1.0 m/s.

Rate of the work done by the rope is power of the rope.

Power\ =\ \dfrac{\Delta W}{\Delta t}\\\Rightarrow P\ =\ \dfrac{\Delta W}{\dfrac{d}{v}}\\\Rightarrow P\ =\ \dfrac{\Delta W\times v}{d}\\\Rightarrow P\ =\ \dfrac{900\times 1.0}{8.0}\\\Rightarrow P\ =\ 112.5\ Watt

Part (c)

  • Initial speed of the skier = v = 2.0 m/s.

Rate of the work done by the rope is power of the rope.

Power\ =\ \dfrac{\Delta W}{\Delta t}\\\Rightarrow P\ =\ \dfrac{\Delta W}{\dfrac{d}{v}}\\\Rightarrow P\ =\ \dfrac{\Delta W\times v}{d}\\\Rightarrow P\ =\ \dfrac{900\times 2.0}{8.0}\\\Rightarrow P\ =\ 225\ Watt

4 0
3 years ago
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