Biomechanics Ch 1-3

Tim and Ben sit on opposite sides of a playground seesaw. Tim sits 1.2m from the axis of the seesaw and Ben sits 1.5m from the axis of the seesaw. Tim's weight is 200N and Ben's body mass is 20kg. (use 9.8m/g2 of gravitational acceleration) (a) How much torque is created at the axis by Tim? (b) How much torque is created at the axis by Ben?

(a) 200N*1.2m = 240Nm (b) 20kg* (9.8m/s2)*1.5m = 294Nm

At take-off of a long jumper, the resultant velocity is 8m/s and take-off angle is 30° from the horizontal ground. Use the following trigonometry values (if needed) for calculation; sin30°=0.5, cos30°=0.87, tan30°=0.58 (a) what is the horizontal velocity of a long jumper? (b) what is the vertical velocity of a long jumper?

(a) 8m/s*cos30° = 6.96m/s (b) 8m/s "sin30° = 4m/s

A 1 cm long section of the Achilles tendon is 1 cm square in cross section. What is the stress in this tendon if it is subjected to a tensile force of 0.2 N?

2000 Pa

How much compressive stress is present on the L1 and L2 vertebra disc of a 600N woman, given that approximately 40% of body weight is supported by the disc when she stands in anatomical position? (Assume that the disc is oriented horizontally and that its surface area is 20 cm^2.)

F=600N*0.40=240N, Area = 20 cm^2 Stress = 240 N/20 cm^2 = 12 N/cm^2

Sarah is out for her daily run. She runs 3 km west, then 4 km south, and then runs on a path that takes her directly back to the place she started. a) how far did she run in Km? b) if she has run at an average speed of 4. m/s, how long did the entire run take in minutes?

a) 3 km+4 km+ 5 km = 12 km b) (12000m)/(4 m/s) = 3000s = 50 min

Gravitational force on planet X is 30% of that found on the earth. If a person weights 490N on earth (use 9.8m/s" of gravitational acceleration) (a) what is the person's weight on planet X? (b) what is the person's mass in [kg] on planet X?

a. 490N*0.3=147N b. 490N/(9.8m/s2) = 50kg

choose the term that describes the application of a single force of sufficient magnitude to cause injury

acute loading

Biomechanical research has contributed to which of the following? A. injury prevention B. enhanced sport performance C. equipment design D. all of the above

all the above

to obtain the least pressure... A. apply a small force spread over a large area B. apply a small force spread over a small area C. apply a large force spread over a large area D. apply a large force spread over a small area

apply a small force spread over a large area

Which of the following statement about the terms is incorrect? A. compression is types of force exerts a squeezing effect on the body B. torque is the rotary effect of a force C. stress is calculated the same as pressure D. bending is a load that produces twisting of a body around its longitudinal axis

bending is a load that produces twisting of a body around its longitudinal axis

a free body diagram includes which of the following? A. sketch of an object, body, or body part being analyzed B. vectors representations of all forces acting on the system C. both A and B D. None of above

both A and B

A bending force can result in which of the following types of stress?

both compression and tension

in a free body diagram of the human body, where would the vector representing weight of the body originate?

center of gravity

which of following is true regarding circumduction?

combines flexion, extension, adduction, and abduction

which of the following terms best describes translational motion along a curved line?

curvilinear

Which of the following is an incorrect pair of term and its unit? A. pressure, N/m2 B. impulse, N-s C. density, kg/m2 D. acceleration, m/s2

density, kg/m2

__________________ is used to describe the motion of bringing the foot closer to the lower leg

dorsiflexion

when a stretched material returns to its original shape, it's called:

elastic

deformation exceeding the structure's yield point produce mechanical failure of the structure

false

force is always a weight

false

pressure is synonymous with weight

false

torsion is the rotary effect of a force

false

which of the following is an incorrect pair of term and its unit? A. torque, N-m B. pressure, N/cm2 C. force, kg-m/s D. weight, N

force, kg/m^2

which of the following are all vector quantities? A. pressure, mass, acceleration B. force, pressure, weight C. force, torque, inertia D. density, acceleration, volume

force, pressure, weight

the frontal plane divides the body into equal ____________

front and back halves

abduction occurs in which plane?

frontal

which of the following is an incorrect pair of the glenohumeral joint movement and the plane of motion that movement can occur? A. abduction - frontal plane B. lateral rotation - transverse plane C. hyperextension - sagittal plane D. horizontal adduction - frontal plane

horizontal adduction - frontal plane

which of the following statement is incorrect? A. inertia is the tendency of a body to resist a change in its state of motion B. inertia is directly proportional to mass and unit of inertia is [g] C. mass is quantity of matter composing a body D. term that describes the mass per unit of volume is density

inertia is directly proportional to mass and unit of inertia is g

which of following terms means "farther from the head"?

inferior

which of the following characteristics of a vector represents magnitude? A. its angle of orientation B. its length C. its direction D. all of these answers are correct

it's length

_____________ is the term that describes the study of the description of motion, including considerations of space and time.

kinematics

which action is not an example of sagittal plane movement? A. flexion B. hyperextension C. lateral flexion D. plantar flexion

lateral flexion

which of following is/are pair (s) of terms and it's SI (metric) unit?

length, mm volume, liter pressure, Pa

movements in the transverse plane occur around which axis?

longitudinal

choose the term that describes the study of the action of forces A. Kinetics B. mechanics C. metric system D. qualitative

mechanics or kinetics

choose the term that describes "toward the midline of the body". A. medial B. posterior C. proximal D. rectilinear

medial

choose the term that describes "toward the back of the body".

posterior

choose the term that describes "involving a nonnumeric description of quality".

qualitative

Which imaginary cardinal plane bisects the body into right and left halves? A. sagittal B. frontal C. transverse D. None of these are correct

sagittal

Which of the following is an incorrect pair of terms of SI units? length - mm speed - ft/sec volume - liter pressure- Pa

speed- ft/sec

which of the following terms is applied to the study of systems in a constant state of motion? A. Dynamics B. Statics C. Anthropometrics D. Plyometrics

statics

in anatomical position, the forearm is in what position?

supinated

Which of following statement is not true? A. the knee is proximal joint relative to the ankle joint B. the shank is distal segment relative to the thigh C. the elbow is proximal joint relative to the shoulder joint D. the knee is distal joint relative to the hip joint

the elbow is proximal joint relative to the shoulder joint

Weight is always a force

true

anatomical reference position is when palms face forward, erect posture, starting position for describing motion

true

compression is types of force exerts a squeezing effect on the body

true

impulse is the product of force and the time over which the force acts

true

inertia is the tendency of a body to resist a change in its state of motion

true

mass is quantity of matter composing a body

true

shear force act parallel to a surface

true

stress is calculated the same as pressure

true

term that describes the mass per unit of volume is density

true

the knee is proximal joint relative to the ankle joint

true

the shank is distal segment relative to the thigh

true

torque is the rotary effect of a force

true

10kg ball in free fall is subjected to a crosswind exerting a force of 20N and to a vertical air resistance force of 38N. What is the square of magnitude of resultant force acting on the ball (use 9.8m/s? of gravitational acceleration)?

vertical : (9.8*10)N - 38N = 60N horizontal : 20N 60^2 + 20^2 = 4000