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3 years ago

What do signal trainees do

Physics

1 answer:

Evgen [1.6K]3 years ago

8 0

Answer:

A signal apprentice works for a rail company, learning the duties of a signal maintainer through on-the-job training and experience. As part of this apprenticeship, you work on a railway to assist a seasoned signal maintainer as they install, repair, inspect, and test signal equipment.

Explanation:

You might be interested in

The muzzle velocity of a bullet fired from a new rifle is 100 m/s. Neglecting air resistance, at the end of one second a bullet

Burka [1]

Answer:

C. (100+4.9)m

Explanation:

u = 100m/s, t = 1 sec, g = 9.8m/s^2

s = ut + 1/2gt^2

s = 100×1 + 1/2×9.8×1^2 = 100+4.9

s = (100+4.9)m

8 0

3 years ago

a. What proportion of resistors have resistances less than 90 Ω? b. Find the mean resistance. c. Find the standard deviation of

Anettt [7]

Answer:

a) 0.0625 = 6.25%

b) 106.67 Ω

c) 9.43 Ω

d) 1

Explanation:

The probability distribution is given as

f(x) = (x - 80)/800 for 80 < x < 120

f(x) = 0 otherwise.

f(x) = (x/800) - (0.1)

a) Proportion of resistors with resistance less than 90 Ω

P(X < 90) = ∫⁹⁰₈₀ f(x) dx

∫⁹⁰₈₀ f(x) dx = ∫⁹⁰₈₀ [(x/800) - (0.1)]

= [(x²/1600) - 0.1x]⁹⁰₈₀

= [(90²/1600) - 0.1(90)] - [(80²/1600) - 0.1(80)]

= (5.0625 - 9) - [4 - 8]

= -3.9375 + 4 = 0.0625 = 6.25%

b) The mean is given by the expected value expression E(X) = = Σ xᵢpᵢ (with the sum done all over the data set for each variable and its corresponding probability)

It can be written in integral form as

Mean = ∫¹²⁰₈₀ xf(x) dx (with the integral done all over the probability function, i.e. from, 80 to 120)

Mean = ∫¹²⁰₈₀ x[(x/800) - (0.1)] dx

= ∫¹²⁰₈₀ [(x²/800) - (0.1x)] dx

= [(x³/2400) - (0.05x²)]¹²⁰₈₀

= [(120³/2400) - (0.05(120²)] - [(80³/2400) - (0.05(80²)]

= [720 - 720] - [213.33 - 320] = 106.67 Ω

c) Standard deviation = √(variance)

Variance = Var(X) = Σx²p − μ²

μ = mean = expected value = 106.67 Ω

Σx²p = ∫¹²⁰₈₀ x²f(x) dx = ∫¹²⁰₈₀ x² [(x/800) - (0.1)] dx = ∫¹²⁰₈₀ [(x³/800) - (0.1x²)] dx

= [(x⁴/3200) - (0.0333x³)]¹²⁰₈₀

= [(120⁴/3200) - (0.0333(120³)] - [(80⁴/3200) - (0.0333(80)³)]

= (64800 - 57600) - (12800 - 17066.667)

= 11466.667

Variance = 11466.667 - 106.67² = 88.85

Standard deviation = √88.85 = 9.43 Ω

d) Cdf = sum of probabilities over the entire probability function

Cdf = ∫¹²⁰₈₀ f(x) dx = ∫¹²⁰₈₀ [(x/800) - (0.1)] dx

= [(x²/1600) - 0.1x]¹²⁰₈₀ = [(120²/1600) - 0.1(120)] - [(80²/1600) - 0.1(80)] = (9 - 12) - (4 - 8) = -3+4 = 1 as it should be!!!

Hope this Helps!!!

4 0

4 years ago

How fast must a 2.70-g ping-pong ball move in order to have the same kinetic energy as a 145-g baseball moving at 31.0 m/s

Helen [10]

Answer:

227 m/s

Explanation:

Kinetic energy formula:

$\displaystyle \text{KE} = \frac{1}{2} mv^2$

where m = mass of the object (kg)
and v = speed of the object (m/s)

Let's find the kinetic energy of the 145-g baseball moving at 31.0 m/s.

First convert the mass to kilograms:

145-g → 0.145 kg

Plug known values into the KE formula.

$\displaystyle \text{KE} = \frac{1}{2} (.145)(31.0)^2$
$\displaystyle \text{KE} = 69.6725 \ \text{J}$

Now we want to find how fast a 2.70-g ping pong ball must move in order to achieve a kinetic energy of 69.6725 J.

First convert the mass to kilograms:

2.70-g → 0.00270 kg

Plug known values into the KE formula.

$\displaystyle 69.6725 = \frac{1}{2} (.00270)v^2$
$\displaystyle \frac{2(69.6725)}{.00270} =v^2$
$57609.25926=v^2$
$v=227.1767137$

The ping-pong ball must move at a speed of 227 m/s to achieve the same kinetic energy as the baseball.

4 0

3 years ago

Friction is generated when?

valkas [14]

Things are rubbed against each other

8 0

3 years ago

ring a race a swimmer completes two laps. The first lap is From point A to B; the second is from B to A. Each lap is 60 meters l

cupoosta [38]

Answer:

Total time to complete the race = 45 sec

Explanation:

We have given that each lap is 60 m long

Average speed for the first lap = 2 m/sec

So time taken to complete the first lap $time\ t=\frac{distance}{speed}=\frac{60}{2}=30sec$

Average speed for second lap = 2 m/sec

So time taken to cover the second lap $time\ t=\frac{distance}{speed}=\frac{60}{4}=15sec$

So total time to complete the race = 30 +15 =45 sec

4 0

3 years ago