PHY 105 Test 1 May 16, 2002 30 minutes

La Salle University

Dr. R. A. DiDio

1. A person on a diet loses 2.3 kg per week. Express this mass loss rate in milligrams per second. (10 pts)

Solution:

2. Porous rock through which groundwater can move is called an aquifer. The volume V of water that moves through a cross section of area A of the aquifer in time t is given by Darcy’s Law:

In this equation H is the vertical drop of the aquifer over the horizontal distance L. Use dimensional analysis to determine the SI units of K, the hydraulic conductivity of the aquifer. (10 pts)

Solution: Noting that the dimensions of V and A are L³ and L², respectively, while H and L both have dimensions of length, the dimensions of K must be:

In SI, this is m/s.

3. A car is driven east for a distance of 50 km, then north for 30 km, and then in a direction 30^o west of north for 20 km. (15 pts)

a) Sketch a vector diagram of this itinerary. Label your vectors, and show the Resultant vector.

b) Calculate the magnitude and direction of the resultant vector. Does your answer agree with the resultant draw in (a)?

· This result appears to match the geometrical sketch of part (a) because:

^· The magnitude of R from the graph should be > 30 and < 100. The angle should be more than 45⁰