Answer:
α = -0.01625 rad / s²
Explanation:
This is an exercise in angular kinematics, we can use the relation
w = w₀ + 2 α θ
linear and angular variables are related
v = w r
w = v / r
Let's reduce the magnitudes to the SI system
v₀ = 91 km / h (1000m / 1km) (1h / 3600s) = 25.278 m / s
v = 48 km / h = 13,333 m / s
θ = 75 rev (2π rad / 1 rev) = 471.24 rad
Let's find the angular velocities
w₀ = v₀ / r
w₀ = 25.278 / 0.78
w₀ = 32,408 rad / s
w = v / r
w = 13.333 / 0.78
w = 17.09 rad / s
we calculate the angular acceleration
α = (w- w₀) / 2θ
α = (17.09 - 32.408) / (2 471.24)
α = -0.01625 rad / s²
the negative sign indicates that the wheel is stopping
Answer:
It inflicted psychological harm on children.
The correct answer is entropy.
In fact, second law of thermodynamics states that the total entropy of an isolated system can never decrease. It can remain constant if the system is in equilibrium or in case of a reversible process: however, perfectly reversible process do not exist in the real world, so the entropy of a system always increases whenever there is a process that involves energy changes.
Answer:
D. 2
Explanation:
The skydiver will reach terminal velocity when gravity = air resistance. When this occurs, he/she will no longer accelerate and his/her speed will be constant.
Once the skydiver opens the parachute, his/her speed will decrease suddenly, and again the air resistance increases due to the parachute's large area. Eventually, gravity will equal air resistance again and terminal velocity will be reached for the second time.
Even though the speeds are different, the first terminal velocity is much higher than the second one, this question refers to how many times terminal velocity is reached, not how many times the skydiver accelerates.