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docker41 [41]
4 years ago
11

Which statement about the speed of light is true?

Physics
1 answer:
kolezko [41]4 years ago
5 0
' B ' is the only true one.
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A yet-to-be-built spacecraft starts from Earth moving at constant speed to the yet-tobe-discovered planet Retah, which is 20 lig
Gre4nikov [31]

Answer:

The  time elapsed at the spacecraft’s frame is less that the time elapsed at earth's  frame

Explanation:

From the question we are told that

The distance between earth and Retah is  d = 20 \ light \ hours =  20 * 3600 *  c =  72000c \ m

Here c is the peed of light with value c =  3.0*10^8 m/s

The time taken to reach Retah from earth is  t =  25 \ hours  =  25 * 3600 =90000 \ sec

The velocity of the spacecraft is mathematically evaluated  as

     v_s =  \frac{d }{t}

substituting values

   v_s =  \frac{72000 * 3.0*10^{8} }{90000}

    v_s =  2.40*10^{8} \ m/s

The time elapsed in the spacecraft’s frame is mathematically evaluated as

      T  =  t *  \sqrt{ 1 -  \frac{v^2}{c^2} }

substituting value

       T  =  90000 *  \sqrt{ 1 -  \frac{[2.4*10^{8}]^2}{[3.0*10^{8}]^2} }

        T = 54000 \ s

=>    T  = 15 \ hours

So  The  time elapsed at the spacecraft’s frame is less that the time elapsed at earth's  frame

       

7 0
3 years ago
A box that is resting on an inclined plane has what forces acting on it
miskamm [114]

A box residing on an inclined plane has following forces:

In the X- direction

Mg sin (theta) = horizontal  component of weight of the box

f = Frictional force = uN , u = frictional factor, N= mg

In the Y- direction

upward force = Normal reaction of the box = mg

downward force = mg cos(theta) = vertical component of weight of the box


5 0
4 years ago
a Porsche 911 accelerates from rest to 27 metre per second due north in 5.8 seconds the mass of the car is 1400 kg what is the m
user100 [1]

Answer:

The average force has a magnitude 6524 N due north.

Explanation:

The average net force F = ma where m = mass of car = 1400 kg and a = acceleration.

a = (v - u)/t where u = initial velocity of car = 0 m/s (since it starts from rest)

v = final velocity of car = 27 m/s due north and t = time of motion = 5.8 s

a = (27 m/s - 0 m/s)/5.8 s = 27 m/s ÷ 5.8 s = 4.66 m/s

Since the direction of the velocity change is the direction of the acceleration, the acceleration is 4.66 m/s due north.

The average force, F = ma = 1400 kg × 4.66 m/s = 6524 N

Since the acceleration is due north, the average force takes the direction of the acceleration.

So the direction of the average force is due north

The average force has a magnitude 6524 N due north.

7 0
3 years ago
Can someone please help me with this
Mekhanik [1.2K]

Answer:

B because the earth rotational axis tilt away from the sun.

3 0
3 years ago
A machine with a 5-N input force and a 25-N output force has a mechanical advantage of?
jolli1 [7]
So we want to know the mechanical advantage of a machine that has 5 N input force and 25 N out force. Mechanical advantage Ma is the measure of force amplification of some machine. We calculate it by taking the ratio of the output force Fo over the input force Fi. Ma=Fo/Fi=(25 N)/(5 N)=5. So Mechanical advantage for our machine is Ma=5 and the correct answer is the second one. 
8 0
3 years ago
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