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3 years ago

PLEASE HURRY! The highest speed ever achieved on a bicycle was reached by John Howard of the United

Physics

2 answers:

Yuki888 [10]3 years ago

4 0

Answer:

Say, the speed of the bicycle before it was decelerated is 245 km/h. Then, John would like to decrease his bicycle's speed by 20%. That means, after the deceleration, he still has 80% of the initial speed.

Let's find out how fast is 80% of the initial speed.

80% * 245 km/h = 196 km/h

So let's say, the terminal speed of the bicycle (after deceleration) is 196 km/h.

Find the difference between the initial speed and terminal speed:

245 km/h - 196 km/h = 49 km/h

Now change the unit of km/h to m/s:

49 km/h = 49 / 3.6 m/s = 13.61 m/s

now determine the time needed to decelerate 20% of the initial speed.

time (t) = difference of velocity (ΔV) / deceleration (d)

t = 13.61 m/s / -3.00 m/s^2

t = 4.537 seconds

Explanation:

smart

pashok25 [27]3 years ago

3 0

Well, to begin with, your first number gang somewhat aglay. The land speed record that John Howard set on his bicycle in 1985 was 152.2 miles per hour, which works out to 68.04 m/s. So I can see where you got the 6 and the 8 from, but your little decimal point snuck over one place when you weren't looking.

I'll use your number to answer the question. If my solution turns out to be wrong, then it's because you copied the number wrong, and you'll have to work it out again with an initial speed of 68.1m/s.

Initial speed = 6.81 m/s

Final speed = 5.44 m/s

Amount of slowing down = 1.37 m/s

Rate at which the brakes slow you down = 3 m/s each second

Time needed to slow down 1.37 m/s = (1.37 m/s) / (3 m/s^2)

That's 0.457 second. (obviously absurd)

If initial speed = 68.1 m/s

Then amount of slowing down = 62.66 m/s

Time needed at -3 m/s^2 = (62.66/3)

That's 20.9 seconds. Much more reasonable.

By the way, John Howard's record was broken 10 yrs later, in 1995 .

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Johnson made a hole at the bottom of a plastic bottle containing water. However, he noticed that the water did not flow out from

Sphinxa [80]

Answer:

a) See explanation below

b) At X.

Explanation:

Please, see the picture attached with the image of the plastic bottle for this question.

(a) Explain why the water could not flow out of the bottle.

What makes the water flow out of the botlle is the force of gravity, whic attracts the water towards the Earth.

When Johnson made a small hole at the bottom of the plastic bottle containing water, the air outside the bottle, which surrounds it and exerts a pressure all over the outer walls of the bottle, exerted a force against the small area of water "over" the hole that is in contact with the air.

Thus, this force of the air pushing upward through the wall opposed the force of gravity pulling downward making the net force zero and the water cannot fall.

(b) To make the water flow out more easily, his teacher suggested making another hole. At which position - X, Y or Z, should he make the 2nd hole in order for the water to flow out the fastest?

You must open the hole at a place where there is not water but air, such that the outer air can enter in the bottle.

That will make that the pressure in the space over the water inside the bottle be equal to the pressure outside.

The pressure of the air above the water will push it downward. Now, the force from the pressure of air inside the water, which is downward, opposes the upward force from the pressure of air around the first hole, and the net force will be downward, making the water flow out more easily.

Thus, the position where he should make the second hole in order for the water to flow fastest is at X.

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4 years ago

Each corner of a right-angled triangle is occupied by identical point charges "A", "B", and "C" respectively. Draw a sketch of t

NISA [10]

Answer:

Fnet = F√2

Fnet = kq²/r² √2

Explanation:

A exerts a force F on B, and C exerts an equal force F on B perpendicular to that. The net force can be found with Pythagorean theorem:

Fnet = √(F² + F²)

Fnet = F√2

The force between two charges particles is:

F = k q₁ q₂ / r²

where

k is Coulomb's constant, q₁ and q₂ are the charges, and r is the distance between the charges.

If we say the charge of each particle is q, then:

F = kq²/r²

Substituting:

Fnet = kq²/r² √2

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3 years ago

Many industries are powered via distant power stations. Calculate the current flowing through a 7,300m long 10. copper power lin

Oliga [24]

Answer:

Current, I = 1000 A

Explanation:

It is given that,

Length of the copper wire, l = 7300 m

Resistance of copper line, R = 10 ohms

Magnetic field, B = 0.1 T

$\mu_o=4\pi \times 10^{-7}\ T-m/A$

Resistivity, $\rho=1.72\times 10^{-8}\ \Omega-m$

We need to find the current flowing the copper wire. Firstly, we need to find the radius of he power line using physical dimensions as :

$R=\rho \dfrac{l}{A}$

$R=\rho \dfrac{l}{\pi r^2}$

$r=\sqrt{\dfrac{\rho l}{R\pi}}$

$r=\sqrt{\dfrac{1.72\times 10^{-8}\times 7300}{10\pi}}$

r = 0.00199 m

$r=1.99\times 10^{-3}\ m=2\times 10^{-3}\ m$

The magnetic field on a current carrying wire is given by :

$B=\dfrac{\mu_o I}{2\pi r}$

$I=\dfrac{2\pi rB}{\mu_o}$

$I=\dfrac{2\pi \times 0.1\times 2\times 10^{-3}}{4\pi \times 10^{-7}}$

I = 1000 A

So, the current of 1000 A is flowing through the copper wire. Hence, this is the required solution.

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3 years ago

Jake drops a book out of a window from a height of 10 meters. At what velocity does the book hit the ground?

user100 [1]

G = 9.81 m/sec^2) g = 9.81 $\frac{meters}{ second^{2} }$

Solving for velocity : 

$velocity^{2}$ = 2gh 
v = $2gh^{ \frac{1}{2} }$
v = (2 x 9.81 x 10)^1/2 
v = 196.2 m/sec (answer)

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4 years ago

When a object slows down what direction is the force going?

trapecia [35]

Answer: when a object gets slowed down, it's force is either going into friction and drag, if it's on the ground, and weight+drag+friction, if it's in the air.

Explanation:

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3 years ago