I think that the angular velocity vector points at right angles to the direction in which the wheels are turning (spindle on an old fashioned record player ?) and so at right angles to the direction the bike is moving in. This contributes to the gyroscope effect on the wheels and bike and allows a rapidly rotating wheel to be more stable than a slowly rotating one. Problem for the trainee cyclist is to believe that they are actually more stable when their wheels are moving quickly. 'cos the tendency is to go slowly to start with, which makes balancing harder.
But then, most cyclists, especially youngsters, don't sit down all day analysing circular motion vectors, which may be just as well.
Answer:
air resistance, gravitational force
The answers are as follows:
61. Deltoid muscle is the muscle that is located at the rounded contour of the shoulder. The muscle is made up of three different type of fibers, which are anterior, middle and posterior fibers. The anterior deltoid connects the collar bone to the humerus.
The primary function of the anterior fibers is flexion and medial rotation of the arm. The primary function of the middle fibers is abduction of arm and the primary function of the posterior fiber is the extension and lateral rotation of the arm.
62. Adductor muscles are muscles that draw a part of the body towards its median line or towards the axis of an extremity. These muscles can be found in the thigh, foot and hand. The abductor muscles is made up of the following muscles:
a. Adductor brevis: its primary function is the adduction of thigh at the hip joint. It also assist in flexion and medial rotation of the femur at the hip joint.
b. Adductor longus: its primary function is the adduction of thigh at the hip joint. It assist also in flexion and medial rotation of the femur at the hip joint.
c. Adductor magnus: its primary function is the adduction of the thigh. It assists in lateral rotation of the thigh.
d. Gracillis muscle: its primary function is adduction of the thigh. It also assists in flexion of the knee and medial rotation of the flexed knee.
e. Pectineus muscle: Primary function is adduction of thigh. Assists in flexion of thigh.
63. Erector spinae muscles are bundles of paired muscles and tendons which extend through the thoracic, lumbar and the cervical region. These muscles are divided into three groups, which are:
a. Spinallis muscles: primary function is the extension of the head. Also rotate the head.
b. Longissimmus muscles: primary function is extension of the spine. Assist in lateral flexion of the spine.
c. Lliocostalis muscles: primary function is extension of the spine. Assist in lateral flexion of the spine.
64. Rectus abdomini is the paired muscle, which runs vertically on each side of the anterior wall of human abdomen. The muscle is made up of two parralle muscles which are separated by connective tissues. The primary function of the muscle is flexion of the vertebra column. Assists in compression of abdominal wall.
