4. Which scientist proposed the theory that the Moon formed from fission? (5 points)

What is the energy of a photon of ultraviolet radiation with a frequency of 4.4 × 1015 Hz? Planck’s constant is 6.63 × 10–34

Hunter-Best [27]

Answer:

$2.9\cdot 10^{-18} J$

Explanation:

The energy of a photon is given by:

$E=hf$

where

h is the Planck constant

f is the frequency of the photon

In this problem, we have:

$h = 6.63\cdot 10^{-34} Js$

$f=4.4\cdot 10^{15} Hz$ is the frequency of the photon

Substituting into the equation, we find:

$E=(6.63\cdot 10^{-34} Js)(4.4\cdot 10^{15} Hz)=2.9\cdot 10^{-18} J$

4 0

3 years ago

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While unrealistic, we will examine the forces on a leg when one falls from a height by approximating the leg as a uniform cylind

Leno4ka [110]

Answer:

Part A: 7.75 m/s

Part B: 2330.8 kN

Part C: 24.03 kN

Part D: 4.8 kN

Part E: $1.7\times 10^{9} Dyn/cm^{2}$

Part F: Option D

Bending his legs increases the time over which the ground applies force, thus decreasing the force applied by the ground.

Explanation:

Part A

From the fundamental kinematic equation

$v^{2}=u^{2}+2gh$ where v is the velocity of the man just before hitting the ground, g is acceleration due to gravity, u is initial velocity, h is the height.

Since the initial velocity is zero hence

$v^{2}=2gh$

$v=\sqrt 2gh$

Substituting 10 m/s2 for g and 3 m for h we obtain

$v=\sqrt 2\times 10\times 3 =\sqrt 60= 7.745967\approx 7.75 m/s$

Part B 

Force exerted by the leg is given by

F=PA where P is pressure, F is force, A is the cross-section of the bone

$A=\frac {\pi d^{2}}{4}$

Substituting 2.3 cm which is equivalent to 0.023m for d and $1.7\times10^{8} N/m2$ for P we obtain the force as

$F=PA=1.7\times10^{8}*\frac {\pi (0.023)^{2}}{4}= 2330818.276\approx 2330.8 kN$

Part C

The fundamental kinematic equation is part (a) can also be written as

$v^{2}=u^{2}+2a\triangle x$ and making a the subject then

$a=\frac {v^{2}-u^{2}}{2\triangle x}$ where a is acceleration and $\triangle x$ is the change in length

Substituting the value obtained in part a, 7.75 m/s for v, u is zero and 1cm which is equivalent to 0.01 m for $\triangle x$ then

$a=\frac {7.75^{2}-0^{2}}{2\times 0.01}= 3003.125 m/s^{2}$

Force exerted on the man is given by

$F=ma=80\times 3003.125= 240250 N\approx 24.03 kN$

Part D

The fundamental kinematic equation is part (a) can also be written as

$v^{2}=u^{2}+2a\triangle h$ and making a the subject then

$a=\frac {v^{2}-u^{2}}{2\triangle h}$ where a is acceleration and $\triangle h$ is the change in height

Also, force exerted on the man is given by $F=ma=m\times \frac {v^{2}-u^{2}}{2\triangle h}$

Substituting 80 Kg for m, 50 cm which is equivalent to 0.5m for \triangle h and other values as used in part c

$F=ma=m\times \frac {v^{2}-u^{2}}{2\triangle h}=80\times \frac {7.75^{2}-0^{2}}{2\times 0.5}= 4805 N\approx 4.8 kN$

Part E

$P=1.7\times 10^{8}=1.7\times 10^{8}\times (\frac {10^{5} Dyn}{10^{4} cm^{2}}=1.7\times 10^{9} Dyn/cm^{2}$

Part F

Bending his legs increases the time over which the ground applies force, thus decreasing the force applied by the ground

7 0

3 years ago

Which of the foolwing best define net force?

DochEvi [55]

Net force can be defined as the sum of force acting on an object in all the directions

.i.e Net force= F acting on a body at upward direction+ F at downward direction+ F at leftward direction+ F at rightward direction.

e.g if a body is at rest the sum of forces acting on body in all direction is zero

but if a body is moving its mean body is facing an unbalanced net force.

8 0

3 years ago

Question

Jobisdone [24]

Answer:

A wavelength is a measure of distance between two consecutive crests or trough. So , the unit of wavelength is same as unit of distance. I.e metre

7 0

3 years ago

What is one way homeostasis benefits living organisms?

kirill115 [55]

Answer:

it maintains balance, it keeps body temperatures , heart rate and all other bodily functions regulated to keep the organism stable when the environment is not.

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3 years ago

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