Answer:
Approximately 
(assuming that the projectile was launched at angle of 
above the horizon.)
Explanation:
Initial vertical component of velocity:
.
The question assumed that there is no drag on this projectile. Additionally, the altitude of this projectile just before landing 
is the same as the altitude 
at which this projectile was launched: 
.
Hence, the initial vertical velocity of this projectile would be the exact opposite of the vertical velocity of this projectile right before landing. Since the initial vertical velocity is 
(upwards,) the vertical velocity right before landing would be 
(downwards.) The change in vertical velocity is:
.
Since there is no drag on this projectile, the vertical acceleration of this projectile would be 
. In other words, 
.
Hence, the time it takes to achieve a (vertical) velocity change of 
would be:
.
Hence, this projectile would be in the air for approximately .
Answer:
a) F = 2.25 10³ N, b) REPULSIVE.
Explanation:
a) The electric force is given by coulomb's law
F = 
k q1q2 / r2
in this case nso indicate that the two charges have the same value
q₁ = q₂ = 2.5 10⁻⁶ C
Let's reduce the magnitudes to the SI system
r = 0.5 cm (1m / 100cm) = 5 10⁻³ m
let's calculate
F = 
F = 2.25 10³ N
b) In electricity, electric charges of the same sign repel and those of the opposite sign attract
In this exercise, the balls are equal and are rubbed with the same material, for which it acquires charges of the same type, consequently, as the charges are of the same type, they indicate that the negative force is REPULSIVE.
Answer:
Support
Posture
Protection
Explanation:
Support – the skeleton keeps the body upright and provides a framework for muscle and tissue attachment.
Posture – the skeleton gives the correct shape to our body.
Protection – the bones of the skeleton protect the internal organs and reduce the risk of injury on impact.
