**Answer:**

I don't really know this one sorry

A. power plants burn coal. A fossil-fuel power plant is one that burns fossil fuels such as coal, natural gas or petroleum (oil) to produce electricity.

b. Fossil fuels are called so because they have been derived from fossils, which were formed millions of years ago during the time of the dinosaurs. They are fossilized organic remains that over millions of years have been converted to oil, gas, and coal.

C. they are generally classified as non-renewable resources because they take millions of years to form and known viable reserves are being depleted much faster than new ones are generated.

5.

a. Gravitational potential energy and work done

If an object is lifted, work is done against the force of gravity.

When work is done energy is transferred to the object and it gains gravitational potential energy.

If the object falls from that height, the same amount of work would have to be done by the force of gravity to bring it back to the Earth’s surface.

If an object at a certain height has 2000 J of gravitational potential energy, we can say that:

2000 J of work has been done in getting the object to that height from the ground

and

2000 J of work would have to be done to bring it back to the ground.

**Answer:**

<em>The mass of the object is 40 Kg</em>

**Explanation:**

<u>Net Force</u>

According to the second Newton's law, the net force exerted by an external agent on an object is:

F = m.a

Where:

a = acceleration of the object.

m = mass of the object.

The mass can be calculated by solving for m:

The object has a net force of F=600 N acting on it and travels at , thus the mas is:

m = 40 Kg

**The mass of the object is 40 Kg**

**Answer:**

1. **E x 4πr² = ( Q x r³) / ( R³ x ε₀ )**

**Explanation:**

According to the problem, Q is the charge on the non conducting sphere of radius R. Let ρ be the volume charge density of the non conducting sphere.

As shown in the figure, let r be the radius of the sphere inside the bigger non conducting sphere. Hence, the charge on the sphere of radius r is :

Q₁ = ∫ ρ dV

Here dV is the volume element of sphere of radius r.

Q₁ = ρ x 4π x ∫ r² dr

The limit of integration is from 0 to r as r is less than R.

Q₁ = (4π x ρ x r³ )/3

But volume charge density, ρ =

So,

Applying Gauss law of electrostatics ;

∫ E ds = Q₁/ε₀

Here E is electric field inside the sphere and ds is surface element of sphere of radius r.

Substitute the value of Q₁ in the above equation. Hence,

**E x 4πr² = ( Q x r³) / ( R³ x ε₀ )**

Microwave because they are powerful and available can be d answer