Does Earth's gravity pull more strongly on a block of wood or on a block or iron having the same size? Neglecting air resistance, which one falls faster when dropped?
A) Gravity pulls more strongly on the iron, and both fall at the same speed.
B) Gravity pulls equally strongly on both, and both fall at the same speed.
C) Gravity pulls equally strongly on both, and the iron falls faster.
D) Gravity pulls more strongly on the iron, and the iron falls faster.
E) None of the above.
Question 2
During a positron emission tomography (PET) scan of the brain,
A) an external positron beam is sent through the patient's brain and detected as it leaves the patient.
B) matter and antimatter annihilate within the brain to create positrons that are detected as they leave the patient.
C) radioactive fluorine creates positrons within the brain that are detected as they leave the patient.
D) positrons and electrons annihilate within the brain to create gamma photons that are detected as they leave the patient.
E) highly sensitive detectors measure the positrons that are naturally emitted by the human body.
Tracheids in conifer wood.
Uranus's aurorae against its equatorial rings, imaged by the Hubble telescope. Unlike the auror
Earth’s history spans 4.5 billion years. Geologists and paleontologists have pieced together the his
Red rocks due to oxidation of iron near the surface
The Last Man on Earth