Answer:
Electric field, 
Explanation:
It is given that,
Mass of sphere, m = 2.1 g = 0.0021 kg
Charge, 
We need to find the magnitude of electric field that balances the weight of a plastic spheres. So,

a = g



or

Hence, the magnitude of electric field that balances its weight is
. Hence, this is the required solution.
Answer:
The pnictogens consist of two non-metals, two metalloids, one metal, and one element with unknown chemical properties. All the elements in the group are solids at room temperature, except for nitrogen which is gaseous at room temperature.
<h2>
Option A is the correct answer.</h2>
Explanation:
Acceleration due to gravity

G = 6.67 × 10⁻¹¹ m² kg⁻¹ s⁻²
Let mass of earth be M and radius of earth be r.
We have

Now
A hypothetical planet has a mass of one-half that of the earth and a radius of twice that of the earth.
Mass of hypothetical planet, M' = M/2
Radius of hypothetical planet, r' = 2r
Substituting

Option A is the correct answer.
Answer:
450 joules ; 450 joules ; 45.9 m
Explanation:
Given that :
Initial Velocity, u = 30m/s
Mass, m = 1 kg
Kinetic Energy of ball (KE) = 0.5mu²
K. E = 0.5 * 1 * 30^2
K.E = 0.5 * 900
K.E = 450 Joules
B.) Potential Energy (P. E)
P. E = mgh
At the highest point, all kinetic energy has would have become potential energy, hence
K. E = P. E = 450 Joules
C) Height of the ball :
From ; P. E = mgh
Where ; g = acceleration due to gravity = 9.8m/s² ; h = height
450 = 1 * 9.8 * h
450 = 9.8h
h = 450 / 9.8
h = 45.918
h = 45.9 m
To find the mass of the planet we will apply the relationship of the given circumference of the planet with the given data and thus find the radius of the planet. From the kinematic equations of motion we will find the gravitational acceleration of the planet, and under the description of this value by Newton's laws the mass of the planet, that is,
The circumference of the planet is,

Under the mathematical value the radius would be



Using second equation of motion

Replacing the values given,

Rearranging and solving for 'a' we have,

Using the value of acceleration due to gravity from Newton's law we have that

Here,
r = Radius of the planet
G = Gravitational Universal constant
M = Mass of the Planet


Therefore the mass of this planet is 