4A: Let’s picture an adventurous rock-climber hanging at the edge of a cliff. Gravity is providing a downward force. The only reason he does not fall down to the valley below is due to the force of tension upward, provided by the muscles of his arm. You will work through some interesting real-world problems involving tensile forces in these tutorials.
The second part to the complicated problem. We figure out the tension in the wire connecting the two masses. Then we figure our how much we need to accelerate a pie for it to safely reach a man's face.