Pulleys, Strings, Springs and Things Part 2

Pulleys, Strings, Springs and Things Part 2 Physics Springs Chapter 6 Blue Springs (Deland, FL)

Pulleys, continued…

Forces and Pulleys Free-body Diagram F T T Mg

Pulleys can get complex. The principle stays simple.

Example 6-7aAtwood’s Machine

a a m2g - T = a T-m1g = a Example 6-7bAtwood’s Machine

Simple Springs

Simple Spring Fling If the spring constant is K, free length is L0, what is L? L0 L Here’s the free-body diagram: F= -K(L-L0) M F= -Mg

Springy Thingy Each spring produces a force according to F= -Kx. What is the force of two springs in “parallel”, for the same displacement x? Dx

0 / 100 Force of Parallel Springs Each spring produces force F=kx for displacement x. What is the force of two springs in parallel for displacement x? • Total force is –Kx, since each spring force remains the same. • Total force is ½ (-Kx), since each spring carries ½ the total weight. • Total force is 2(-Kx), since each spring exerts (-Kx). Cross-Tab Label

Force of Springs in “Series” F = -K1Dx Dx/2 F = -K1Dx Dx/2 Dx

What is the force of 2 springs in “series”, each with spring constant K, for same displacement x? 0 / 100 • The force is just F = -K Dx, since each spring has the same force constant. • The force is twice as large. • The force is half as big, F = (1/2)(-K Dx) Cross-Tab Label

Spring “Series” F= -K Dx/2 F = -K1Dx Dx/2 F= -K Dx/2 F = -K1Dx Dx/2 Dx F= -(K/2) Dx

Pulleys, Strings, Springs and Things Part 2