I think you need more information like the force of gravity and the force of the three people. Once you combine the two, however, you should get the net force.
B = 0.018 T Ans,
Since, it is moving in a circular path, thus, centripetal force will act on it i.e.
F =

where, m is the mass of the object, v is the velocity and r is the radius of circular path.
And, since a positive charge is moving, it will create magnetic force which is equal to F = qvB
where q is the charge, v is the velocity of the particle and B is the magnetic field.
Now, the two forces will be equal,
i.e.

= qvB
⇒

= qB
⇒B =

<span>putting the values, we get,
</span>
use q = 1.6 * 10^ -19
⇒ B = 0.018 T
Answer:
30.63 m
Explanation:
Using y = ut + 1/2gt² where u = initial speed of block = 0 m/s, g = acceleration due to gravity = 9.8 m/s² and t = time of fall = 2.5 s and y = height of fall.
So, substituting the values of the variables into the equation, we have
y = ut + 1/2gt²
y = 0 m/s × 2.5 s + 1/2 × 9.8 m/s² × (2.5 s)²
y = 0 m + 4.9 m/s² × 6.25 s²
y = 0 m + 30.625 m
y = 30.625 m
y ≅ 30.63 m
So, the brick fell 30.63 m