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Andre45 [30]
4 years ago
11

A bicyclist was moving at a rate of 8 m/s, and then sped up to 10 m/s. If the cyclist has a mass of 120 kg, how much work was ne

eded to increase his velocity? (Hint: Use the work-kinetic energy theorem.)
Physics
2 answers:
Vera_Pavlovna [14]4 years ago
7 0

Answer:

Work = 2160 J

Explanation:

As per work energy theorem we know that work done is equal to the change in the kinetic energy of the cyclist.

As the cyclist is initially moving at speed 8 m/s and after some time his speed changes to 10 m/s

So here we can say that

final kinetic energy - initial kinetic energy = work done

W = \frac{1}{2}m(v_f^2 - v_i^2)

now by plug in all values

W = \frac{1}{2}(120)(10^2 - 8^2)

W = 2160 J

so work done by cyclist will be 2160 J

sergeinik [125]4 years ago
3 0
W=∆KE

KE=1/2m∆v^2

=1/2*120*(10-8) ^2

=240j
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A visible light has a wavelength of 727.3 nm. Determine its frequency, energy per photon, and color.
Snezhnost [94]

Answer:

f=4.12\times 10^{14}\ Hz and E=2.73\times 10^{-19}\ J

Explanation:

The wavelength of a visible light is 727.3 nm.

727.3\ nm=727.3 \times 10^{-9}\ m

The formula is as follows :

c=f\lambda

f is the frequency of the visible light

f=\dfrac{c}{\lambda}\\\\f=\dfrac{3\times 10^8}{727.3 \times 10^{-9}}\\\\f=4.12\times 10^{14}\ Hz

Energy of a photon is given by :

E = hf, h is Planck's constant

E=6.63\times 10^{-34}\times 4.12\times 10^{14}\\\\E=2.73\times 10^{-19}\ J

Red color has a frequency of 4.12\times 10^{14}\ Hz and energy per photon is 2.73\times 10^{-19}\ J.

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3 years ago
12. Bacteria are grown in a petri dish. One side of the dish is sprayed with an antibiotic. After a week, the number of bacteria
Talja [164]

what's the question here?

4 0
3 years ago
Light in vacuum is incident on the surface of a slab of transparent material. In the vacuum the beam makes an angle of 39.9° wit
wariber [46]

Answer:

n=2.053

Explanation:

We will use Snell's Law defined as:

n_{1}*Sin\theta_{1}=n_{2}*Sin\theta_{2}

Where n values are indexes of refraction and \theta values are the angles in each medium. For vacuum, the index of refraction in n=1. With this we have enough information to state:

1*Sin(39.9)=n_{2}*Sin(18.2)

Solving for n_{2} yields:

n_{2}=\frac{Sin(39.9)}{Sin(18.2)}=2.053

Remember to use degrees for trigonometric functions instead of radians!

6 0
3 years ago
A small fan has blades that have a radius of 0.0600 m. When the fan is turned on, the tips of the blades have a tangential accel
zhuklara [117]

Answer:

α = 395 rad/s²

Explanation:

Main features of uniformly accelerated circular motion

A body performs a uniformly accelerated circular motion   when its trajectory is a circle and its angular acceleration is constant  (α = cte). In it the velocity vector is tangent at each point to the trajectory and, in addition, its magnitude varies uniformly.

There is tangential acceleration (at) and is constant.

at = α*R     Formula (1)

where

α  is the angular acceleration

R is the radius of the circular path

There is normal or centripetal acceleration that determines the change in direction of the velocity vector.

Data

R = 0.0600 m   :blade radius

at = 23.7 m/s² : tangential acceleration of the blades

Angular acceleration of the blades (α)

We replace data in the formula (1)

at = α*R  

23.7 = α*(0.06)

α = (23.7) / (0.06)

α = 395 rad/s²

7 0
3 years ago
What is the weight of a 45 kg box?
8_murik_8 [283]
45 kg.Hope it helps! :)
4 0
3 years ago
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