A(n)___ forms where light seems to come from.

Streak is a reliable identifier of a mineral. true or false

inysia [295]

Answer:

true?

Explanation:

Im positive but not 100% sure wait for someone else to answer and see if they say the same.

8 0

3 years ago

Read 2 more answers

When a 70 kg man sits on the stool, by what percent does the length of the legs decrease? Assume, for simplicity, that the stool

allochka39001 [22]

The diameter of one leg of the stool is missing and it's 2cm.

Answer:

(ΔL/L) = 0.00729%

Explanation:

If the Weight of the man is W, the weight will be distributed equally on the 3 legs and so the reactions for each leg will be W/3 or F/3.

Now, Youngs modulus(Y) of douglas fir wood is about 1.3 x 10^(10) N/m^2. Gotten from youngs modulus of common materials.

Now, weight of man is 70kg.

Now diameter of one leg is 2cm.so radius of one leg = 2/2 = 1cm = 1 x 10^(-2)m

Area for one leg is; π( 1 x 10^(-2)m)^2 = 3.14 x 10^(-4)m

Now as stated earlier, the force on one leg is; F/3.

Now F = mg = 70 x 9.81 = 686.7N

So, force on one leg = 686.7/3 = 228. 9N

Now we know youngs modulus(Y) = Stress/Strain.

Stress = F/A while Strain = ΔL/L

Therefore Y = (F/A) / (ΔL/L)

And therefore, (ΔL/L) = F/(AY)

So (ΔL/L) = 228.9/(3.14 x 10^(-4))x(1.3 x 10^(10)) = 7. 29 x 10^(-5)

When expressed in percentage, it becomes 0.00729%

7 0

3 years ago

An object with a mass of 25 kg object is moving at 30 m/s. What is the

Pani-rosa [81]

Answer: 750 kgm/s

Explanation:

Mass of object = 25 kg

Speed by which object moves =30 m/s. Linear momentum of the object = ?

Since momentum refers to the quantity of motion of the moving object,

Linear momentum = Mass x Speed

= 25kg x 30m/s

= 750 kgm/s

Thus, the linear momentum of the object is 750 kgm/s

7 0

3 years ago

A microwave oven operates on the principle that application of a high-frequency field causes electrically polarized molecules su

Tema [17]

Answer:

a

The time it would take the beef to reach a temperature of 0⁰C is t= 662 sec = 11.93 min

b)

The time it would take to heat the beef to uniform temperature of 80⁰C is

t = 365 sec =5.93 min

c

Efficient absorption of Microwave power is in regions of liquid water . Hence if the food or the microwave irradiation is not uniform, the power will be absorbed non-uniformly, resulting in a non-uniform temperature rise. Defrost region will absorb more energy per unit volume than frozen region.if food is of low thermal conductivity, there will be insufficient time for heat conduction to make the temperature more uniform.Use of low power allows more time for conduction to occur.

Explanation:

The explanation is shown on the first second and third uploaded image