11. In everyday use and in kinematics, the speed of an object is the magnitude of the rate of change of its position with time or the magnitude of the change of its position per unit of time; it is thus a scalar quantity.
12. Speed is the time rate at which an object is moving along a path, while velocity is the rate and direction of an object's movement. Put another way, speed is a scalar value, while velocity is a vector. In its simplest form, average velocity is calculated by dividing change in position (Δr) by change in time (Δt).
13. Here we will learn the mathematical relation between the speed, distance and time. The speed of a moving body is the distance travelled by it in unit time. If the distance is in km and time is in hours, then the speed is km/hr. If the distance is in m and the time is in seconds, then the speed is m/sec.
14. Average speed is the distance traveled divided by elapsed time. We have noted that distance traveled can be greater than displacement. So average speed can be greater than average velocity, which is displacement divided by time
15. Both have the same average speed, so neither is the fastest. (Please see the solution in the picture)
16. Acceleration is a vector quantity which is defined as the rate at which an object changes its velocity. An object is accelerating if it is changing its velocity.
A medical researcher measured the diastolic wall thicknesses of the arteries in a young, healthy test subject. The test subject came back 20 years later to have the measurements repeated. The measurements revealed that the subject's artery walls were half as thick as they were originally. Which of the following is the most likely long-term effect if the measured trend continues?
b) Arteries will be unable to withstand the pressure exerted by the heart, causing an aneurysm
Answer:
a maybe correct me if im wrong
Answer:
C The sarcomere is contracted, and the actin and myosin filaments are completely overlapped.
Explanation:
In rest, the tropomyosin inhibits the attraction strengths between myosin and actin filaments. Contraction initiates when an action potential depolarizes the inner portion of the muscle fiber. Calcium channels activate in the T tubules membrane, releasing calcium into the sarcolemma. At this point, tropomyosin is obstructing binding sites for myosin on the thin filament. When calcium binds to troponin C, troponin T alters the tropomyosin position by moving it and unblocking the binding sites. Myosin heads join the uncovered actin-binding points forming cross-bridges, and while doing so, ATP turns into ADP and inorganic phosphate, which is released. Myofilaments slide impulsed by chemical energy collected in myosin heads, producing a power stroke. The power stroke initiates when the myosin cross-bridge binds to actin. As they slide, ADP molecules are released. A new ATP links to myosin heads and breaks the bindings to the actin filament. Then ATP splits into ADP and phosphate, and the energy produced is accumulated in the myosin heads, which starts a new binding cycle to actin. Finally, Z-bands are pulled toward each other, shortening the sarcomere and the I-band, producing muscle fiber contraction.
In the sarcomere, which is the contractile unit of skeletal muscles, there are
- Thick myosin myofilaments in the central region belonging to the A band.
- Thin filaments united to the Z lines, extending in the interior of the A band until they reach the border of the H band.
- Thin actin filaments composing the I band, which belong to two sarcomeres adjacent to a Z line.
When the muscle contracts, the muscular fiber gets shorter and thicker due to the reduction in the length of the sarcomere. The H line and the I band get shorter. The Z lines get closer to the A band, meaning that they get closer to each other. A band keeps constant in length. This change is produced by movement mechanisms that involve a change in the relative position of actin and myosin filaments.
