Answer:
A
B

C

D

Explanation:
Considering the first question
From the question we are told that
The spring constant is 
The potential energy is 
Generally the potential energy stored in spring is mathematically represented as 
=>
=>
=>
Considering the second question
From the question we are told that
The mass of the dart is m = 0.050 kg
Generally from the law of energy conservation

=> 
=> 
Considering the third question
The height at which the dart was fired horizontally is 
Generally from the law of energy conservation

Here KE is kinetic energy of the dart which is mathematical represented as

=> 
=> 
=> 
Considering the fourth question
Generally the total time of flight of the dart is mathematically represented as

=> 
=> 
Generally the horizontal distance from the equilibrium position to the ground is mathematically represented as

=> 
=> 
Density = Mass/Volume
So, given mass = 20 g and volume = 40 cm^3
By substituting in above equation, Density = 20/40 = 0.5 g/cm^3
Hope it helps.
Gravity ALWAYS does that, and electrostatic force does it when two objects have opposite charges.
Answer:
The galaxies outside of our own are moving away from us, and the ones that are farthest away are moving the fastest. This means that no matter what galaxy you happen to be in, all the other galaxies are moving away from you
Explanation:
Given:
B =
T
V=
q = 2.5 ×
C
α = 90
To find:
Force = ?
Formula used:
Force on the moving charge is given by,
F = q V B sin α
Where F = force exerted on moving charge
V = velocity of charge
q = charge
α = angle between direction of V and B
Solution:
F = q V B sin α
Where F = force exerted on moving charge
V = velocity of charge
q = charge
α = angle between direction of V and B
F = 
F = 37.5 × 
F = 3.75 Newton
Thus, the force acting on the moving charge is 3.75 Newton.