Answer:
The 10-meter long rod of an SR-71 airplane expands 0.02 meters (2 centimeters) when plane flies at 3 times the speed of sound.
Explanation:
From Physics we get that expansion of the rod portion is found by this formula:
(Eq. 1)
Where:
- Expansion of the rod portion, measured in meters.
- Linear coefficient of expansion for titanium, measured in
.
- Initial length of the rod portion, measured in meters.
- Initial temperature of the rod portion, measured in Celsius.
- Final temperature of the rod portion, measured in Celsius.
If we know that
,
,
and
, the expansion experimented by the rod portion is:


The 10-meter long rod of an SR-71 airplane expands 0.02 meters (2 centimeters) when plane flies at 3 times the speed of sound.
The car's (average) acceleration would be

The car's position over time would be given by

so that after 2.4 seconds, the car will have traveled a distance of


Examples of physical properties include: color, shape, size, density, melting point, and boiling point.
Answer:
B. They are inversely proportional to the square of the distance.
Explanation:
The gravitational force between two objects is given by:

where
G is the gravitational constant
m1, m2 are the masses of the two objects
r is the distance between the two objects
While the electrical force is given by

where
k is the Coulomb's constant
q1, q2 are the charges of the two objects
r is the distance between the two objects
As we see from the two equations, both forces are inversely proportional to the square of the distance, so the correct option is
B. They are inversely proportional to the square of the distance.
Remember Coulomb's law: the magnitude of the electric force F between two stationary charges q₁ and q₂ over a distance r is

where k ≈ 8,98 × 10⁹ kg•m³/(s²•C²) is Coulomb's constant.
8.1. The diagram is simple, since only two forces are involved. The particle at Q₂ feels a force to the left due to the particle at Q₁ and a downward force due to the particle at Q₃.
8.2. First convert everything to base SI units:
0,02 µC = 0,02 × 10⁻⁶ C = 2 × 10⁻⁸ C
0,03 µC = 3 × 10⁻⁸ C
0,04 µC = 4 × 10⁻⁸ C
300 mm = 300 × 10⁻³ m = 0,3 m
600 mm = 0,6 m
Force due to Q₁ :

Force due to Q₃ :

8.3. The net force on the particle at Q₂ is the vector

Its magnitude is

and makes an angle θ with the positive horizontal axis (pointing to the right) such that

where we subtract 180° because
terminates in the third quadrant, but the inverse tangent function can only return angles between -90° and 90°. We use the fact that tan(x) has a period of 180° to get the angle that ends in the right quadrant.