A 15 kg box sits still on a rough inclined plane (no math required here).

Which term describes a substance that has a low melting point and poor electrical conductivity?

densk [106]

Answer:Simple Covalent substance

Explanation:Simple covalent substance describes a substance that has a low melting point and poor electrical conductivity because:

(1)melting point :For the covalent bond and intermolecular force that are present in a simple covalent substance,energy is needed to break the forces of attraction present. In the simple covalent substance, little energy is needed because the intermolecular forces present are broken because they are weaker compared to the covalent bond present.

Therefore, when simple covalent substance melts,only the intermolecular forces are broken leaving only the covalent bond in the substance.

(2) poor conductivity: for a substance to conduct electricity,it must have charged particles which are free to move to and fro.

But in the simple covalent substance,there are no charged particles that can be separated due to the covalent bond present in simple covalent substance.

4 0

3 years ago

Gretchen runs the first 4.0 km of a race at 5.0 m/s. Then a stiff wind comes up, so she runs the last 1.0 km at only 4.0 m/s.

KIM [24]

Answer:

The velocity is $v = 4.76 \ m/s$

Explanation:

From the question we are told that

The first distance is $d_1 = 4.0 \ km = 4000 \ m$

The first speed is $v_1 = 5.0 \ m/s$

The second distance is $d_2 = 1.0 \ km = 1000 \ m$

The second speed is $v_2 = 4.0 \ m/s$

Generally the time taken for first distance is

$t_1 = \frac{d_1 }{v_1 }$

$t_1 = \frac{4000}{5}$

$t_1 = 800 \ s$

The time taken for second distance is

$t_1 = \frac{d_2 }{v_2 }$

$t_1 = \frac{1000}{4}$

$t_1 = 250 \ s$

The total time is mathematically represented as

$t = t_1 + t_2$

=> $t = 800 + 250$

=> $t = 1050 \ s$

Generally the constant velocity that would let her finish at the same time is mathematically represented as

$v = \frac{d_1 + d_2}{t }$

=> $v = \frac{4000 + 1000}{1050 }$

=> $v = 4.76 \ m/s$

7 0

4 years ago

Sana loved swimming.She joined a new smimmimg club .When she looked at the floor of the pool to estimate its depth she found tha

melisa1 [442]

Answer:

Refraction

Explanation:

When light passes from a rarer medium into a denser medium, it bends in the medium away from the normal. This creates the phenomenon of "apparent depth" as given in the question.

6 0

2 years ago

When an exothermic reaction releases thermal energy, this energy is usually_____.

saw5 [17]

Explanation:

A chemical reaction in which heat or energy is released is known as an exothermic reaction.

On the other hand, when two objects are placed together and heat flows from hotter object to colder object then this process is known as conduction. Therefore, energy is dissipated in conduction process.

Since energy released released goes into the atmosphere and is not used anywhere.

Thus, we can conclude that when an exothermic reaction releases thermal energy, this energy is usually not useable to do work and it is dissipated by conduction.

8 0

3 years ago

A block pushed along the floor with velocity V0 slides a distance d after the pushing force is removed. a) if the mass of the bl

KengaRu [80]

Answer:

$a) \ d_2=d_1\\b) \ d_2=4d_1$

Explanation:

Assume that the distance travelled initially is d.

In order to stop the block you need some external force which is friction.

If we use the law of energy conservation:

$E_i=E_f\\\frac{mv^2}{2}= E_{Friction}\\E_{Friction}=F_{Friction}*d\\F_{Friction}= \mu_kmg\\\frac{mv^2}{2}= \mu_kmgd\\ d=\frac{v^2}{2\mu_kg}$

a)

Looking at the formula you can see that the mass doesn't affect the distance travelled, as lng as the initial velocity is constant (Which indicates that the force must be higher to push the block to the same speed) therefore the distance is the same.

b) If the velocity is doubled, then the distance travelled is multiplied by 4, because the distance deppends on the square of the velocity.

6 0

4 years ago