Answer:
A. Refer to the figure.
B. The net force acting on the crate is

C. We should first find the acceleration of the crate using the following kinematics equation:

Mass of the crate can be found by Newton’s Second Law:
Answer:
r₁ = 20.5 cm
Explanation:
In this exercise we can use the conservation of energy
the gravitational power energy is always attractive, the electrical power energy is repulsive if the charges are of the same sign
starting point.
Em₀ = U_g + U_e + K =
the two in the kinetic energy is because they are two particles
final point. When it is detained
Em_f = U_g + U_e =
the energy is conserved
Em₀ = em_f
the charges and masses of the two particles are equal
sustitute the values
-6.67-11 (4.5 10-3) ² / 0.25 - 9, 109 (30 10-9) ² / 0.25 + 4.5 10-3 4² = - 6.67 10- 11 (4.5 10-3) ² / r1 -9 109 (30 10-9) ² / r1
-5.4 10⁻¹⁵ + 3.24 10⁻⁵ - 7.2 10⁻⁵ = -1.35 10⁻¹⁵ / r₁ + 8.1 10⁻⁶ / r₁
We can see that the terms that correspond to the gravitational potential energy are much smaller than the terms of the electric power, which is why we depress them.
3.24 10⁻⁵ - 7.2 10⁻⁵ = 8.1 10⁻⁶ / r₁
-3.96 10⁻⁵ = 8.1 10⁻⁶ / r₁
r₁ = 8.1 10⁻⁶ /3.96 10⁻⁵
r₁ = 2.045 10⁻¹ m
r₁ = 20.5 cm
Answer:
the average velocity of the ball is 5 m/s.
Explanation:
Given;
initial position of the ball, x₁ = 12 m East
final position of the ball, x₂ = 8 m West
initial time of motion, t₁ = 10.0 s
final time of motion, t₂ = 6.0 s
The average velocity is calculated as follows;

let the Eastward direction be positive
Let the westward direction be negative

Therefore, the average velocity of the ball is 5 m/s.