A 4.00-kg object is attached to a vertical rod by two strings. The object rotates in a horizontal circle at constant speed 6.00 m/s. What is the tension in the upper string and the lower string.

Well your missing information here, in order to compute the centripetal force you must have the radius or distance seperating these two strings.

3 meters is the total distance 1.5 for each one

To find the tension in the upper and lower strings, we need to consider the forces acting on the object. In this case, the only force acting on the object is the tension in the strings, which provides the centripetal force required to keep the object moving in a horizontal circle.

Let's use the following variables:
- m: mass of the object (4.00 kg)
- v: velocity of the object (6.00 m/s)
- T1: tension in the upper string
- T2: tension in the lower string
- R: radius or distance of the object from the rotation point (missing information)

To find the tension in the strings, we will use the centripetal force equation:

F_c = m * a_c

Since the object moves in a horizontal circle with constant speed, the acceleration is the centripetal acceleration (a_c = v^2 / R).

Rearranging the equation, we can express the centripetal force (F_c) in terms of the tensions:

F_c = T1 + T2

Substituting the acceleration and mass into the centripetal force equation, we get:

m * (v^2 / R) = T1 + T2

To solve for the tensions, we need the value of R. Once you provide the radius or distance separating the two strings, we can calculate the values of T1 and T2 using the above equation.