Answer:
A- The ball has both kinetic and potential energy,
Explanation:
kinetic energy by virtue of its motion.
potential energy by virtue of its position. (It could roll off the edge of the tabel and convert gravity potential energy to kinetic energy)
Answer:
a) attractiva, b) dF =
, c) F =
, d) F = -1.09 N
Explanation:
a) q1 is negative and the charge of the bar is positive therefore the force is attractive
b) For this exercise we use Coulomb's law, where we assume a card dQ₂ at a distance x
dF =
where k is a constant, Q₁ the charge at the origin, x the distance
c) To find the total force we must integrate from the beginning of the bar at x = d to the end point of the bar x = d + L
∫ dF =
as they indicate that the load on the bar is uniformly distributed, we use the concept of linear density
λ = dQ₂ / dx
DQ₂ = λ dx
we substitute
F = 
F = k Q1 λ (
)
we evaluate the integral
F = k Q₁ λ
F = k Q₁ λ 
we change the linear density by its value
λ = Q2 / L
F =
d) we calculate the magnitude of F
F =9 10⁹ (-4.2 10⁻⁶)
F = -1.09 N
the sign indicates that the force is attractive
Wooden desk it doesn’t conduct or absorb heat as much as metal or plastic