BIOD43H3 Lecture Notes - Lecture 7: Elastic Energy
BIOD43 Lecture 7 Notes: Movement on Land II
• Experiment of horses walking on treadmill: when horses walked on incline, the horses
needed to accelerate their center of mass. Horse rare legs push more forward
• Overall, incline has more vertical force
• Smaller animals generally have more crouched legs, compared to large animals. Ex.
Elephants have stiff and extended legs. This is because when the ground makes contact
with jointed appendages, the ground reaction forces act to apply torque to the joints.
• Moment Arm= the perpendicular distance from axis to the vector of force
• The greater the distance from the pivot point means less force is needed to get object to
move. Ex. Trying to move unscrew a knob with fingers is much more difficult than
unscrewing the knob with a wrench (moment arm), which adds greater length.
• Larger animals must adopt a more upright posture to applying less pressure, as their
center of mass is better distributed.
• Overall velocity scales increase with larger animals
• Smaller animals have stronger bone structure relative to their size compared to larger
mammals, such as humans and elephants. Ex. If a mouse was dropped a distance 2x its
od height the affet ouldt e as great if a elephat dropped 2 its distae.
BIOD43 Lecture 8- Movement on Land
Wh at the iggest aials ru the fastest?
Animals reach their max speed over short sprints, not long distances. Short sprints are powered
aerobically, meaning the fuel that powers the muscles comes from short-term storage and is
limited.
- Mass has to overcome inertia for an animal to move, a elephat at urst ito a
sprint as quickly as a mouse
- Larger animals run out of energy supplied by the muscles not being able to reach their
theoretically possible maximum speed.
Compressive and Bending Strength of Bone
-Stregth durig opressio or edig doest sale uh ith aial size.
-Force at failure is constant
-Peak stresses when duty cycles are low can be multiples of weight.
-Peak bone stresses are mass independent
Larger anials hae a saller Safet fator ith respet to ehaial failure of oes uder
load.
-Limbs can be modeled as mass-springs
Mass-Spring Properties of Terrestrial Locomotion
1) During walking= Rotation component is obvious
= Very little compression
2) During Running = Compression + Rotational component is obvious (greatest at mid-
stance)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Experiment of horses walking on treadmill: when horses walked on incline, the horses. Biod43 lecture 7 notes: movement on land ii needed to accelerate their center of mass. Horse rare legs push more forward: overall, incline has more vertical force, smaller animals generally have more crouched legs, compared to large animals. If a mouse was dropped a distance 2x its (cid:271)od(cid:455) height the affe(cid:272)t (cid:449)ould(cid:374)(cid:859)t (cid:271)e as great if a(cid:374) elepha(cid:374)t dropped 2 (cid:454) its dista(cid:374)(cid:272)e. Animals reach their max speed over short sprints, not long distances. Short sprints are powered aerobically, meaning the fuel that powers the muscles comes from short-term storage and is limited. Mass has to overcome inertia for an animal to move, a(cid:374) elepha(cid:374)t (cid:272)a(cid:374)(cid:859)t (cid:271)urst i(cid:374)to a sprint as quickly as a mouse. Larger animals run out of energy supplied by the muscles not being able to reach their theoretically possible maximum speed. Stre(cid:374)gth duri(cid:374)g (cid:272)o(cid:373)pressio(cid:374) or (cid:271)e(cid:374)di(cid:374)g does(cid:374)(cid:859)t s(cid:272)ale (cid:373)u(cid:272)h (cid:449)ith a(cid:374)i(cid:373)al size.
