An ideal battery creates a potential difference at the electrodes equal to its emf no matter what is attached. However, in reality, the electrochemical cells that creates the emf has its own internal resistance. In the circuit below the dashed box represents a real battery, and Rb is the internal resistance. It causes the battery output voltage (that you would measure between the top and bottom of the box) to be different from the emf. In this circuit, the emf is 9 V, the internal resistance is 2 Ω , R1 = 15 Ω , R2 = 10 Ω , and R3 = 20 Ω . a. What is the battery's output voltage in V with the switch open?
b. What is the battery's output voltage in V with the switch closed?

There is a theory that indicates that dinosaurs became extinct when about 65 million years ago, a large asteroid hit the earth surface. dust caused by this collision blocked the sunlight reaching the earth's surface and many forms of life became extinct due to the cold. fearing this threat, how large the radius of an asteroid should you be looking for if the dangerous asteroid size is approximately the same as the one that killed the dinosaurs? available data suggests that about 18% of that asteroid's mass ended up as a dust spread evenly over earth after eventually settling out of the upper atmosphere. about 0.0180 g/cm^2 of dust, which is chemically different than the earth's rock, covered the earth's surface. typical asteroids have a density of about 1.9 g/cm^3. now that we know the size of the asteroid, how much energy was released during impact, assuming all of it was just the kinetic energy of the asteroid right before the impact?

It is really hard for me right know

Abeverage can is made of 3004-h19 aluminum alloy (elastic modulus 69 gpa, tensile yield strength 285 mpa, density 2.72 g/cm^3). the dimensions on the can are approximated as a thin-walled cylinder with a height of 4.83 inches, diameter of 2.60 inches. empty the can has a mass of 14.2 g. determine: a. the wall thickness of the cylinder b. assuming a pinned-pinned condition what is the critical load? c. assuming a fixed-fixed condition what is the critical load?