Answer:
She exerts a force of 40 N.
Explanation:
The fact that the ring remains stationary indicates that the forces are in equilibrium.
Let’s denote Jo's force as x.
The equation to consider is
140 = x + 100
x = 40
Utilizing the equation F = ma, where F represents the force applied by the machine, A denotes acceleration (equivalent to v/t, with v as velocity and t as time), and M symbolizes mass, we can calculate as follows: F = mv/t. Thus, F = (0.15kg) (30 – 0 m/s) / 0.5 s, resulting in F = 9 N.
2 minutes = 120 seconds
120/15 = 8
The black horse corresponds to 8 seconds.
1) The projectile's motion follows
,

In order to determine the velocity, we must compute the derivative of h(t):
Next, we will compute the speed at t=2 s and t=4 s:
The negative value of the second speed suggests that the projectile has already attained its highest point and is now descending.
2) The maximum height of the projectile occurs when its speed equals zero:
Thus, we have
And solving yields

3) To determine the maximum height, we substitute the time at which the projectile reaches this peak into h(t), specifically t=2.30 s:
4) The time at which the projectile lands is when the height reaches zero; h(t)=0, which leads to
This results in a second-degree equation, producing two answers: the negative root can be disregarded as it lacks physical significance; the second root is

, which indicates the landing time of the projectile.
5) The moment the projectile impacts the ground corresponds to the velocity at time t=4.68 s:

, carrying a negative sign to denote a downward direction.