4. estimate the time necessary for the spread of the south atlantic ocean between africa and south america by dividing the present separation along the trace of the red dashed line on figure 11.2 by the rate of spreading as calculated in question 2. ritter, scott. interpreting earth history: a manual in historical geology (p. 159). waveland press, inc.. kindle edition.

Scientists use laser range-finding to measure the distance to the moon with great accuracy. a brief laser pulse is fired at the moon, then the time interval is measured until the "echo" is seen by a telescope. a laser beam spreads out as it travels because it diffracts through a circular exit as it leaves the laser. in order for the reflected light to be bright enough to detect, the laser spot on the moon must be no more than 1.0 km in diameter. staying within this diameter is accomplished by using a special large-diameter laser. part a if λ = 540nm , what is the minimum diameter of the circular opening from which the laser beam emerges? the earth-moon distance is 384,000 km. express your answer to two significant figures and include the appropriate units.

A500g object falls off a cliff and losers 100 j from its gravitational potential energy store. if the gravitational field strength g=9.8n/kg, how high is the cliff?

An artificial satellite circles the earth in a circular orbit at a location where the acceleration due to gravity is 6.03 m/s^2. determine the orbital period of the satellite.