Concept:
For an object moving in a vertical circle, the forces acting at the highest point are the tension \(T\) acting downwards and the gravitational force \(mg\) acting downwards. The centripetal force required for circular motion is provided by the sum of these forces.
Step 1: Apply the centripetal force equation at the highest point.
The net force toward the center is:
$$ T + mg = \frac{mv^2}{r} $$
Step 2: Substitute the given values.
Given: \( m = 1 \text{ kg} \), \( r = 1 \text{ m} \), \( v = 4 \text{ ms}^{-1} \), and \( g = 10 \text{ ms}^{-2} \).
$$ T + (1 \times 10) = \frac{1 \times (4)^2}{1} $$
$$ T + 10 = 16 $$
Step 3: Solve for tension T.
$$ T = 16 - 10 = 6 \text{ N} $$
$$\boxed{6 \text{ N}}$$