Ask question

Ask question

All categories

3 years ago

6

When were the following metals discovered:

1 answer:

Katen [24]3 years ago

3 0

Answer:

A. 4000 BC

B. January 24, 1848

C. 1400 BC

Explanation:

Please mark brainliest.

You might be interested in

I need to name 20 gases in physics

Oliga [24]

Easy ! EVERY element and every compound melts, then boils and becomes a gas, if you heat it to a high enough temperature. That includes iron, gold, water, salt, glass, almost any substance.

4 0

4 years ago

How did Edwin Hubble's discovery that the Andromeda Nebula was at least 1 million light years away change scientists' view of th

masha68 [24]

After years of observation, Hubble made an extraordinary discovery. In 1923 he spotted a Cepheid variable star in what was known as the Andromeda Nebula. Using Leavitt's techniques, he was able to show that Andromeda was nearly 1 million light years away and clearly a galaxy in its own right, not a gas cloud.

4 0

3 years ago

A steel playground slide is 5.25 m long and is raised 2.75 m on one end. A 45.0 kg child slides down from the top starting at re

Temka [501]

Answer:

$F=32.24N$

Explanation:

From the question we are told that:

Height $h= 2.75 m$

Length $l = 5.25 m$

Mass $m=45kg$

Final speed $v_f=6.81$

Generally the equation for Potential Energy P.E is mathematically given by

$P.E=mgh$

Therefore

Initial potential energy

$P.E_1=45*9.8*2.75 \\\\P.E_1= 1212.75 J$

Generally the equation for Kinetic Energy K.E is mathematically given by

$K.E=0.5mv^2$

Therefore

Final kinetic energy

$K.E_2= 1/2*45*6.81*6.81 \\\\K.E_2= 1043.46J$

Generally the equation for Work_done is mathematically given by

$W=P.E_1-K.E_2\\\\W=169.3$

Therefore

$F=\frac{W}{d}\\\\F=\frac{169.3}{5.25}$

$F=32.24N$

8 0

3 years ago

A magnetic field is aligned perpendicular to the plane of a circular loop of wire with radius 5.0 cm and 20 turns. The magnetic

Mariana [72]

Answer:

$V = 0.157(-36 e^{-3t} + 1.5)$

$t = 1.24 s$

Part b)

$EMF = 0.136(-36e^{-3t} + 1.5)$

Explanation:

magnetic field due to external source is given as

$B = 12 e^{-3t} + 1.5 t + 6$

area of the loop is given as

$A = \pi r^2$

$A = \pi(0.05)^2$

$A = 7.85 \times 10^{-3} m^2$

Now we have

$\phi = NBAcos0$

$\phi = (20)(12e^{-3t} + 1.5t + 6)(7.85 \times 10^{-3})$

$V = \frac{d\phi}{dt}$

$V = 0.157\frac{d}{dt}(12e^{-3t} + 1.5t + 6)$

$V = 0.157(-36 e^{-3t} + 1.5)$

now we need to find the time at which voltage is 0.1 Volts so we have

$0.1 V = 0.157(-36e^{-3t} + 1.5)$

$t = 1.24 s$

Part b)

If magnetic field is inclined at an angle of 30 degree with the normal of the loop then

$\phi = NBAcos30$

now we know that induced EMF is given as

$EMF = \frac{d\phi}{dt}$

$EMF = NAcos30\frac{dB}{dt}$

$EMF = (20)(7.85 \times 10^{-3})cos30(\frac{d}{dt}(12e^{-3t} + 1.5t + 6))$

$EMF = 0.136(-36e^{-3t} + 1.5)$

7 0

3 years ago

Two protons are 9.261 fm apart. (1 fm= 1 femtometer = 1 x 10^-15 m.) What is the ratio of the electric force to the gravitationa

Strike441 [17]

Answer:

$1.24\times 10^{36}$

Explanation:

$q$ = magnitude of charge on each proton = 1.6 x 10⁻¹⁹ C

$m$ = mass of each proton = 1.67 x 10⁻²⁷ kg

r = distance between the two protons = 1 x 10⁻¹⁵ m

Electric force between the two protons is given as

$F_{e} = \frac{kq^{2}}{r^{2}}$

$F_{e} = \frac{(9\times 10^{9})(1.6\times 10^{-19})^{2}}{(1\times 10^{-15})^{2}}$

$F_{e} = 230.4$ N

Gravitational force between the two protons is given as

$F_{g} = \frac{Gm^{2}}{r^{2}}$

$F_{g} = \frac{(6.67\times 10^{-11})(1.67\times 10^{-27})^{2}}{(1\times 10^{-15})^{2}}$

$F_{g} = 1.86\times 10^{-34}$ N

Ratio is given as

$Ratio =\frac{F_{e}}{F_{g}}$

$Ratio =\frac{230.4}{1.86\times 10^{-34}}$

$Ratio = 1.24\times 10^{36}$

3 0

3 years ago

Read 2 more answers