The main difference is direction. C.
Speed is a scalar quantity, while Velocity is a vector quantity.
Speed is measured without taking into fact direction, but Velocity takes into fact the direction.
Answer: 42.49
Explanation:
To solve this, we need to keep in mind the following:
While the sphere hangs it is under the effect of gravity. It is creating a Angle of 90° taking the roof as a reference.
Gravity can be noted as a Acceleration Vector. The magnitud for Earth's Gravity is a constant: 9.81 
The acceleration of the Van will affect the sphere also, but this accelaration will be on the X-axis and perpendicular to the gravity. Because this two vectors are taking action under the sphere they will create a angle. This angle can be measured as a relation of the two magnitudes.
Tangent (∅) = Opossite Side / Adyacent Side
By trigonometry, we know the previous formula. This formula allows us to find the Tangent of a angle as a relation between the two perpendiculars magnitudes. In this case the Opossite Side will be the Gravity Accelaration, while the Adyancent Side is the Van's Acceleration.
(1) Tangent (∅) = Gravity's Acceleration (G) / Van's Acceleration (Va)
Searching for the Va in (1)
Va = G/Tan(∅)
Where ∅ in this case is equal to 13.0°
Va = 9.81
/ Tan(13.0°)
Va = 42.49
The vans acceleration need to be 42.49
to create an angle of 13° with the Van's Roof
Answer: Please find the answer in the explanation
Explanation:
Under what circumstances does distance traveled equal magnitude of displacement?
When a body's motion is linear in one direction. Or a body moving in a straight line without turning back.
What is the only case in which magnitude of displacement and distance are exactly the same?
When the body is moving in a straight line with without changing direction or without turning back.
We begin by noting that the angle of incidence is the one that's taken with respect to the normal to the surface in question. In this case the angle of incidence is 30. The material is Flint Glass according to the original question. The refractive indez of air n1=1, the refractive index of red in flint glass is nred=1.57, finally for violet in the glass medium is nviolet=1.60. Snell's Law dictates:

Where

differs for each wavelenght, that means violet and red will have different refractive indices in the glass.
In the second figure provided details are given on which are the angles in question,

is the distance between both rays.


At what distance d from the incidence normal will the beams land at the bottom?
For violet we have:

For red we have:

We finally have: