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3 years ago

Describe how light radiation leaves a star, travels through the vacuum of space, and finally is seen by someone on earth.

1 answer:

7 0

Once expelled from a star it travels through space................. i'm actually confused do you mean particles of light?

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A crane motor exerts 3,500 W to lift a load up 5 floors in 25 seconds. How much work did the crane do?

jok3333 [9.3K]

Answer: 87500J

Explanation:

Given that,

Power exerted by crane = 3,500 W

Time taken = 25 seconds

work done by crane = ?

Since power is the rate of work done per unit time, then power is workdone by the crane divided by the time taken.

i.e power = work / time

3,500 W = work / 25 seconds

Work = 3500W x 25 seconds

Work = 87500J

Thus, 87500 joules of work was done by the crane.

4 0

3 years ago

What is the kinetic energy of a 1 kg ball thrown to a height of 10 meters?

Zigmanuir [339]

Answer:

I think it's B

Explanation:

sorry if im wrong

7 0

3 years ago

You do 1,500j of work in using a hammer. the hammer does 825j of work on a nail. what is the efficiency of the hammer?

KATRIN_1 [288]

A tool or machine's work efficiency is represented by the ratio of the amount of energy exerted and the amount of work done by the object. Thus, if you exert 1500 J work and the hammer does 825 J, the work efficiency is

$Efficiency = \frac{825}{1500} = 0.55$
$Efficiency = 55%$

Thus, the efficiency of the hammer is 55%.

Answer: 55%

6 0

3 years ago

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

What are the chemical symbols for the elements: gold, silver, and tin respectively? A) Ag, Au, and Sn

Grace [21]

Answer:

The answer to your question is B) Au, Ag and Sn

Explanation:

This is a brief explanation of the origin of the symbols

Gold: the symbol (Au) comes from the Latin Aurum

Silver: the symbol (Ag) comes from the Latin Argentum

Tin: the symbol (Sn) comes from the Latin Stannum

Titanium has the chemical symbol Ti-

5 0

3 years ago