Question

1. After watching the video on levers, use the law of levers (F x FA = R x RA) to answer the following two questions (3 points each for 6 points):

1. If the biceps brachii (forearm flexion) muscle inserts on the radial tuberosity 3.2 cm from the elbow and the length of the forearm is 32.0 cm, how much weight can be lifted if the biceps can exert 280 lbs of force?

Hint: FA = 3.2 cm and RA = 32.0 cm.

Note: In scientific contexts forces are usually expressed in Newtons (N) and mass is usually expressed in kilograms (kg). Both units can be easily converted to pounds which is what we are more familiar with.

2. In the example above (same FA and RA) if the person is holding 25 lbs at 90 degrees of elbow flexion (parallel to the ground) and the biceps is exerting 240 lbs of force, which of the following statements is true?

   1. The weight will remain stationary (F x FA = R x RA)

   2. The weight will be lifted (F x FA > R x RA)

   3. The weight will be lowered (F x FA < R x RA)

   4. The weight will be thrown directly to the head of a certain professor who makes students do math problems

Answer 1

Cinen A = 3.2cm, Faco Ra=32com F= 260 lbs , R=2 AS FAXF=RAR R= FAXE RA - 3.2x280 - 32 weight lifted. R = 28/ubs FA AF=240lbs - RA R=28 lbs True (a) weight remain stationary (EX EA = RX RA) True (6) Weight will be lifted if (FAXE) > (RAXR) True CC weight will be lowered (AxF CRAXR) FAXF= 240x3.2= 768 lbs RAXR = 25x32 = 800 lbs True lowered as (RAXR) > (FAXF) option-(C) The weight will be (FX FA <RXRA)