Astudent measures the gravitational acceleration g to be 9.76±0.07 m/s2. to improve his precision he spend a whole day repeating the measurement 400 times. he states the mean of the 400 measurements g 9.746 m/s2 as his best estimate of g. in the lab g has an accepted value of g- 9.80664 t0.2 m/s2 arising from a precision measurement conducted by geo-physicists in the past.

Which of the following are guidelines to follow for obtaining accurate observations

The ultracentrifuge is an important tool for separating and analyzing proteins. because of the enormous centripetal accelerations, the centrifuge must be carefully balanced, with each sample matched by a sample of identical mass on the opposite side. any difference in the masses of opposing samples creates a net force on the shaft of the rotor, potentially leading to a catastrophic failure of the apparatus. suppose a scientist makes a slight error in sample preparation and one sample has a mass 10 mg larger than the opposing sample. if the samples are 12 cm from the axis of the rotor and the ultracentrifuge spins at 70,000 rpm, what is the magnitude of the net force on the rotor due to the unbalanced samples? ( be thorough on your answer)

Abaseball is thrown from the outfield toward the catcher. when the ball reaches its highest point, which statement is true? (a)its velocity is not zero, but its acceleration is zero. (b) its velocity and its acceleration are both zero. (c) its velocity is perpendicular to its acceleration. (d) its acceleration depends on the angle at which the ball was thrown. (e) none of the above statements are true.