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4 years ago

How is one second time defined in SI system.

Physics

1 answer:

kkurt [141]4 years ago

7 0

Answer:

One second is defined by taking the fixed numerical value of the caesium frequency ∆ν, the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be 9 192 631 770 (9.192631770 x 10⁹ ) cycles of the radiation, when expressed in the unit Hz, which is equal to s−¹.

One second is equal to 1/86,400 of a mean solar day.

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A car moves at a constant velocity of 30 m/s and has 3.6 × 105 J of kinetic energy. The driver applies the brakes and the car st

LekaFEV [45]

The force needed to the stop the car is -3.79 N.

Explanation:

The force required to stop the car should have equal magnitude as the force required to move the car but in opposite direction. This is in accordance with the Newton's third law of motion. Since, in the present problem, we know the kinetic energy and velocity of the moving car, we can determine the mass of the car from these two parameters.

So, here v = 30 m/s and k.E. = 3.6 × 10⁵ J, then mass will be

$K.E = \frac{1}{2} * m*v^{2} \\\\m = \frac{2*KE}{v^{2} } = \frac{2*3.6*10^{5} }{30*30}=800 kg$

Now, we know that the work done by the brake to stop the car will be equal to the product of force to stop the car with the distance travelled by the car on applying the brake.Here it is said that the car travels 95 m after the brake has been applied. So with the help of work energy theorem,

Work done = Final kinetic energy - Initial kinetic energy

Work done = Force × Displacement

So, Force × Displacement = Final kinetic energy - Initial Kinetic energy.

$Force * 95 = 0-3.6*10^{5}\\ \\Force =\frac{-3.6*10^{5} }{95}=-3.79 N$

Thus, the force needed to the stop the car is -3.79 N.

5 0

3 years ago

When a hot metal cylinder is dropped into a sample of water, the water molecules

Rashid [163]

Answer:

I believe the answer is speed up.

Explanation:

this is because when water heats up the molecules move father apart from each other they speed up, eventually causing the water to boll

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3 years ago

What three statements are true about all alloys

Alex73 [517]

1. They are made from metals combined in equal amounts
2. They are good conductors of electricity
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4 years ago

If the direction of the position is north and the direction of the velocity is up, then what is the direction of the angular mom

Kay [80]

Answer:

the direction of angular momentum = EAST

Explanation:

given

Direction of position = r = north

Direction of velocity = v = up

angular momentum = L = m(r x v)

where m is the mass, r is the radius, v is the velocity

utilizing the right hand rule, the right finger heading towards the course of position vector and curl them toward direction of velocity, at that point stretch thumb will show the bearing of the angular momentum.

then L = north x up = East

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3 years ago

the length of the glass at 25°C is 500cm after gaining some heat the final length of the glass becomes 500.9cm determine the tem

Vera_Pavlovna [14]

Hi be positive
Smile all day

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3 years ago

How is one second time defined in SI system.​

How is one second time defined in SI system.