Which of the following is the best definition of autoimmune disease?
1 answer:
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Answer:
The false statement is in option 'd': The center of mass of an object must lie within the object.
Explanation:
Center of mass is a theoretical point in a system of particles where the whole mass of the system is assumed to be concentrated.
Mathematically the position vector of center of mass is defined as
where,
is the position vector of the mass dm.
As we can see for homogenous symmetrical objects such as a sphere,cube,disc the center of mass is located at the centroid of the shapes itself but in many shapes it is located outside the body also.
Examples of shapes in which center of mass is located outside the body:
1) Horseshoe shaped body.
2) A thin ring.
In many cases we can make shapes of bodies whose center of mass lies outside the body.
Answer:
= ( ρ_fluid g A) y
Explanation:
This exercise can be solved in two parts, the first finding the equilibrium force and the second finding the oscillating force
for the first part, let's write Newton's equilibrium equation
B₀ - W = 0
B₀ = W
ρ_fluid g V_fluid = W
the volume of the fluid is the area of the cube times the height it is submerged
V_fluid = A y
For the second part, the body introduces a quantity and below this equilibrium point, the equation is
B - W = m a
ρ_fluid g A (y₀ + y) - W = m a
ρ_fluid g A y + (ρ_fluid g A y₀ -W) = m a
ρ_fluid g A y + (B₀-W) = ma
the part in parentheses is zero since it is the force when it is in equilibrium
ρ_fluid g A y = m a
this equation the net force is
= ( ρ_fluid g A) y
we can see that this force varies linearly the distance and measured from the equilibrium position
Answer:
Surely Achilles will catch the Tortoise, in 400 seconds
Explanation:
The problem itself reduces the interval of time many times, almost reaching zero. However, if we assume the interval constant, then it is clear that in two hours Achilles already has surpassed the Tortoise (20 miles while the Tortoise only 3).
To calculate the time, we use kinematic expression for constant speed:
The moment that Achilles catch the tortoise is found by setting the same final position for both (and same time as well, since both start at the same time):