Physics of Fishing: The Pendulum

Recently, I accompanied my daughter to a science museum for a school field trip. Part of one display made me think about fishing: the pendulum. A pendulum is a swinging object on the end of a line.

Beginning anglers learn about the pendulum when they attempt to land fish. Often I observe novices reel in too much line, and then like a carrot dangling in front of a horse, they can’t reach the fish without setting down the rod. If they will leave line out about the length of the rod and lift the tip, the fish will come swinging in for a quick photo and release.

Bait suspended a couple of feet below a bobber is a pendulum which can complicate casting for beginners and even intermediate skill anglers. The cast should be a wide, sweeping motion to prevent the two varying weights from traveling at different speeds and perhaps coming in contact with each other and tangling.

Professional tournament bass anglers are aware of the physics of the pendulum and use it in several ways. One application is when landing a big fish, they will “swing” it into the boat. They use the forward momentum of the fish and lift into the boat, all in one fluid well-timed motion.

When working a heavy jig with a baitcaster reel, especially in vegetation, you may notice pros on fishing shows that quickly strip some line off the reel after a cast. Similarly with a spinning reel, when the lure hits the water and before the bail is closed, the angler quickly lifts the rod high one extra time. This helps the lure fall straight down and thus cover more water. Without this extra few feet of line deployed as the lure enters the water, the line would be tight and the lure would drop but immediately start to swing toward the angler/boat and thus not reach target depth and location.

Don’t let your kids tell you they don’t like the subject of physics. The next time you take your kids fishing, point out some of the forces involved with casting and landing fish. In fact, maybe I’ll suggest that for the next school field trip.

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