Answer:
Assuming the typical saw used to saw boards in home construction and renovation is a circular saw, the diameter of the blade can be estimated as 7-10 inches (17.8-25.4 cm). The linear speed in m/s of a point on the rim of the circular saw blade is then approximately: (π × 25.4 cm) × (2600 rev/min) / (60 s/min) = 28.0 m/s.
The answer is b) venus because the period rotation is also referred to as a day so if venus’ period of rotation is 243 [earth] days and its year is 225 [earth] days, then the period of rotation is longer.
Answer:
a. Big Bang Theory explains the beginning of the universe. The entire matter of the universe is believed to be concentrated in a single point. This point had infinite density. At time, t = 0, at the big bang, universe started expanding and cooling down. This theory is most widely accepted theory describing the beginning of the universe. It is not considered as hypothesis because of the evidences received by the scientists- detection of cosmic microwave background, red shift of the light received from the galaxies indicating that universe is expanding.
b. Cosmic Microwave background radiation is a faint radiation having average temperature of 3 K detected every where around from the sky. This is a residual radiation from 400,000 years after the beginning of the universe. The universe was very hot and dense at the beginning and thus, opaque. Hence, detection of the CMB has provided the evidence of Big bang theory.
c. Scientists have proposed three models of the universe:
1. closed universe- The universe has finite volume and curves around itself. The space-time has positive curvature.
2. open universe - The universe has infinite volume and has a negative curvature.
3. flat universe - The universe has zero curvature. It has infinite volume. The actual density of the universe is equal to the critical density of the universe. The expansion rate slows down over time. This is the most widely accepted model.
The answer is C. Any physical property can be observed without changing the identity of the substance. That’s one of the main things that separates a physical and chemical property.
First, it is necessary to calculate the energy consumed by the bulb during the weekend:
(It is important to express time in seconds).
The energy associated with water is gravitational potential energy and we can write this type of energy depending on volume of water:
Clearing volume in the previous equation: