1 University of District of Columbia: Fall 2016 Semester University Physics II: Physics 202: Homework Set #2 Due: 11/01/2016 Problem #1 : 1D Kinematics : Relative Motion The diagram shows a snapshot at time t=0 of the two balls (Red and Green) on a collision course. At t=0, the balls are separated by a distance D=12m. The Green ball moves with a constant velocity V G= 6 m/s due east, while the red ball moves with constant velocity (VR) =2 m/s due west. [10] (a) Take the origin to be the position of red ball and positive direction to the east. Determine the equation for the displacement (x) of green ball with respect to time (t) in the reference frame of red ball? VG= 6m/s due east (VR)=2 m/s due west D=12 m Green Ball Red Ball (b) Plot the equation for the displacement of the Green ball in a graph up to the scale? ------------------------------------------------------------------------------------------------------------------------------------ 2 Problem # 2: Relative Motion Three Swimmers can swim equally fast relative to the stream of water. They have a race to see who can swim across a river in the least amount of time. [10] Relative to the water, (a) Beth swims perpendicular to the flow, (b) Ann swims upstream at 30o, and (c) Carley swims downstream at 30o. Calculate the velocities of all the 3 girls crossing the river assuming their initial velocity (v0) as 2 m/s? Who gets across the river first ? ------------------------------------------------------------------------------------------------------------------------------------ 3 Problem # 3: Newton’s Laws of Motion: Free body Diagram A block of mass (m2) slides on a table pulled by a string attached to a load (m1) hanging over a frictionless pulley over the side as shown. The coefficient of kinetic friction between the sliding block and table is [µk]. Develop a suitable free body diagram (FBD) that represents the dynamics of the mass. (i) Find the acceleration (a1) of load (m1) and acceleration (a2) of mass (m2) respectively. Show your work in detail. [5] (i) Find the tension (T1) in the string pulling the load (m1), and tension (T2) in the string attached to the mass (m2) on the table. [5] ------------------------------------------------------------------------------------------------------------------------------------- 4 Problem #4: Electrostatics – Equipotential Surface An electric dipole consists of 2 charges: (1) q1= 12nC and (2) q2=12nC placed 10 cm apart as shown below: [10] Compute the electric potentials at points (a), (b) and (c) respectively. ------------------------------------------------------------------------------------------------------------------------------------- 5 Problem # 5: Electrostatics- Equipotential Surface Given a capacitor with various equipotential surfaces [1,2,3,4] enclosed within the boundaries of parallel plates, as shown in figure: [10] Determine the Potential Difference (δV) and Electric Field Intensities (E) between plates 1-2,1-3,2-3, and 1-4 respectively.
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