Answer: A) 2 B) 4 C) 1
Explanation:
The Electric field from a parallel-plate capacitor is given by:
A) E=Q/(L^2 * ε0) so if we put a charge double the final electric field is double that the original.
B) from the above expression for the electric field, If the size of the plate is double, then the E final is four times weaker that the original.
C) If the distante between plates is doubled the final electric field is the same that initial.
C I believe is the correct answer. Developing possible solutions would be easier than spending hours researching or identifying the need.
Answer:
h = 2 R (1 +μ)
Explanation:
This exercise must be solved in parts, first let us know how fast you must reach the curl to stay in the
let's use the mechanical energy conservation agreement
starting point. Lower, just at the curl
Em₀ = K = ½ m v₁²
final point. Highest point of the curl
= U = m g y
Find the height y = 2R
Em₀ = Em_{f}
½ m v₁² = m g 2R
v₁ = √ 4 gR
Any speed greater than this the body remains in the loop.
In the second part we look for the speed that must have when arriving at the part with friction, we use Newton's second law
X axis
-fr = m a (1)
Y Axis
N - W = 0
N = mg
the friction force has the formula
fr = μ N
fr = μ m g
we substitute 1
- μ mg = m a
a = - μ g
having the acceleration, we can use the kinematic relations
v² = v₀² - 2 a x
v₀² = v² + 2 a x
the length of this zone is x = 2R
let's calculate
v₀ = √ (4 gR + 2 μ g 2R)
v₀ = √4gR( 1 + μ)
this is the speed so you must reach the area with fricticon
finally have the third part we use energy conservation
starting point. Highest on the ramp without rubbing
Em₀ = U = m g h
final point. Just before reaching the area with rubbing
= K = ½ m v₀²
Em₀ = Em_{f}
mgh = ½ m 4gR(1 + μ)
h = ½ 4R (1+ μ)
h = 2 R (1 +μ)
Point X lies on a horizontal line. We can intuitively say that the slope of the graph at point X is 0, therefore the acceleration at point X is 0m/s²
Point Y lies on a downward slanting line. To calculate the slope of that line, let's apply this equation:
m = (y₂-y₁)/(x₂-x₁)
m = slope, (x₁, y₁) and (x₂, y₂) correspond to the coordinates of the line's endpoints.
Given values:
(x₁, y₁) = (7, 5)
(x₂, y₂) = (12, 0)
Plug in and solve for m:
m = (0 - 5)/(12 - 7)
m = -1
The acceleration at point Y is -1m/s²
Choice A
The forces acting on the ball, aside from air friction, would be the force exerted on the ball by the boy when he threw it up, and gravity working against the motion of the ball