Describe how we know that the expansion rate of the Universe is currently accelerating
What will be an ideal response?
A study of type Ia supernovae showed that they are about 25 percent fainter than expected. That must mean they are farther away than expected, given their redshifts. This is strong evidence that the expansion of the Universe is accelerating.
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Suppose you have a 100-watt light bulb that you leave turned on for one minute. How much energy does it use?
A) 6,000 joules B) 6,000 watts C) 100 watts D) 100 joules
In a ballistics test, a 28-g bullet pierces a sand bag that is 30cm thick
If the initial bullet velocity was 55m/s and it emerged from the sandbag moving at 18m/s what was the magnitude of the friction force (assuming it to be constant) that the bullet experienced while it traveled through the bag? A) 1.3 N B) 130 N C) 38 N D) 13 N
An atom in a state with its orbital quantum number l = 1 decays to its ground state (with l = 0). A photon of wavelength 630.000 nm is emitted in the process
When the same process takes place in the presence of an intense magnetic field, the following change in the spectrum is observed. With the magnetic field present, one of the emitted lines observed now has a wavelength of 630.030 nm. Which of the following wavelengths would you expect to be also present? A) 630.060 nm B) 629.970 nm C) 630.090 nm D) 629.910 nm E) 630.120 nm
Identical 8.0-mC point charges are positioned on the x axis at x = ±1.0 m and released from rest simultaneously. What is the kinetic energy of either of the charges after it has moved 2.0 m?
a. 84 mJ b. 54 mJ c. 96 mJ d. 63 mJ e. 48 mJ