Next time you're on a swing (as the bob of a large pendulum) notice how the forces on you and the tension in the ropes of the swing change.
At the top of the each swing the ropes are the loosest - and if you swing very high, then for a moment at the top each swing you are close to being in free fall; with nothing holding you up - just gravity pulling you down.
As you fall the rope pulls you in, with increasing force, trying to keeping you to a circular path.
At the bottom of the swing you are moving the fastest, and the rope (and swing seat) are holding you up - if you're swinging very fast - with more the twice the force of gravity.
As you move up the other side, the rope tension relaxes as you get higher and your speed drops.
The ropes tension is lowest at your highest point - for two reasons; you are stationary so it doesn't need to pull you in to keep you moving in a circle, and gravity isn't pulling directly along the rope - but at an angle - so only a portion of the your weight pulls on the rope (and if you swing up to a right angle - none).