3 Points The half-value layer for lead for g rays from 60Co is 12.8 mm. An electrometer gave a count rate of 35 pulses per second when at a
certain distance from a source, with no lead between source and detector. If 6 mm of lead were then inserted between source and
detector, the count rate (in pulses per second) would be nearest to:
A. 16
OB. 8
OC. 20
D. 25
OE. 75

Aball tossed vertically upward from the ground next to a building passes the bottom of a window 1.8 s after being tossed and passes the top of the window 0.20 s later. the window is 2.0 m high from top to bottom. what was the ball's initial velocity? the unit vector j^ is directed upward. how far is the bottom of the window from the launch position? how high does the ball rise above the launch position?

Apulley with mass mp and a radius rp is attached to the ceiling, in a gravity field of 9.81 m/s2 and rotates with no friction about its pivot.

According to an observer on earth, planet x is stationary. maria and samir depart earth on their spaceships at the same time, each flying at 0.5c. maria flies toward planet x and samir flies in the opposite direction. according to maria, her voyage to planet x takes 9 years. how many years does maria's voyage take according to samir?