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timofeeve [1]
3 years ago
12

Archimedes supposedly was asked to determine whether a crown made for the king consisted of puregold. According to legend, he so

lved this problem by weighing the crown first in air and then in water. Suppose the scale read 7.84 N with the crown in air and 6.84 N when it was in water. What should Archimedes have told the king
Physics
1 answer:
DENIUS [597]3 years ago
4 0

Answer:

the crown was not made of pure gold

Explanation:

Mass of gold = weight in air/ g = 7.84N/10ms-2= 0.784 Kg or 0.8Kg

From Archimedes principle:

Upthrust= weight in air- weight in a fluid

Upthrust= volume × density × g

Note density of water = 1000kgm-3

7.84-6.84= V × 1000kgm-3×10ms-2

V= 1/10000= 1×10-4 m^3

Density = mass/ volume= 0.8/1×10-4

= 8×10^3 Kgm-3

But we know the density of gold to be 19.3 ×10^3 kgm-3

Hence the crown was not made of pure gold

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Light waves from the sun can travel trough outer space and reach the earth
konstantin123 [22]

Answer:

this is true

Explanation:

7 0
3 years ago
A machine part has the shape of a solid uniform sphere of mass 245 g and diameter 4.30 cm . It is spinning about a frictionless
Alla [95]

Answer:

Angular acceleration, \alpha =9.49\ rad/s^2

Explanation:

It is given that,

Mass of the solid sphere, m = 245 g = 0.245 kg

Diameter of the sphere, d = 4.3 cm = 0.043 m

Radius, r = 0.0215 m

Force acting at a point, F = 0.02 N

Let \alpha is its angular acceleration. The relation between the angular acceleration and the torque is given by :

\tau=I\times \alpha

I is the moment of inertia of the solid sphere

For a solid sphere, I=\dfrac{2}{5}mr^2

\alpha =\dfrac{\tau}{I}

\alpha =\dfrac{F.r}{(2/5)mr^2}

\alpha =\dfrac{5F}{2mr}

\alpha =\dfrac{5\times 0.02}{2\times 0.245\times 0.0215}

\alpha =9.49\ rad/s^2

So, its angular acceleration is 9.49\ rad/s^2. Hence, this is the required solution.

3 0
3 years ago
A coil is connected in series with a 12.6 kΩ resistor. An ideal 65.2 V battery is applied across the two devices, and the curren
ivolga24 [154]

To solve the problem, start by applying the concepts related to current in an RL circuit. The current is defined exponentially and using Ohm's law we can put the initial current in terms of the voltage and resistance. Consecutively with the calculated time constant we can find the respective inductance. For the second part we will apply the electrical potential energy connectors to find the amount of stored energy.

PART A)

i = i_0 (1-e^{-t/T})

i = (V/R)(1-e^{-t/T})

0.00402 = (65.2/12600)(1-e^{-0.00402/T})

T = 0.002679s

T = L/R

Inductance can be defined then,

L = RT

L = (12600)(0.002679)

L = 33.75H

PART B) Now the energy is given under the terms:

E = \frac{1}{2}Li^2

E = \frac{1}{2} (33.75)(0.00402)^2

E = 0.0002727J

Therefore the energy stored in the coil at this same moment is 0.0002727J

3 0
3 years ago
At what frequency will a 31.0 mH inductor have a reactance of 637.0 Ω?
Shtirlitz [24]

Answer:

3272.4 Hz

Explanation:

L = 31 mH

XL = 637 ohm

XL = 2 π f L

f = XL / (2 π L)

f = 637 / ( 2 x 3.14 x 31 x 10^-3)

f = 3272.4 Hz

5 0
3 years ago
A race car travels along a section of a track with a constant speed of 100 m/s. If this speed is maintained for 15 minutes, how
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(C)90 km
100x60seconds x 15 minutes/1000metres
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