1. When an electron is placed in an electric field it experience an electric force whose magnitude is 1.6 times its weight, find the magnitude of the electric field.

2. If the distance between the proton and electron in a hydrogen atom is 5.3×10^-¹¹m, show that the coulomb force is about 10^39 times the gravitational force.

3. A particle travels along a straight line with a velocity of v=(4t-3t^2)m/s, where t is in seconds. Determine the position of the particle when t=4s. s(position) is 0 when t=0.

4. The position of a dog running in a park is given by

r = [(0.5ms^-1)t + (0.4ms^-2)t^2]i + (0.02ms^-3)t^3j

A. Determine x and y components of the dog's velocity as a function of time, t.

B. At t=5s, how far is the dog from its initial position?

C. At t=5s, what are the magnitude and direction of the dog's velocity?

5. A point charge q = -0.31 nC is fixed at the origin. Where must an electron be placed in order for the electric force acting on it to be exactly opposite to its weight? (Let the y axis be vertical and the x axis be horizontal.)

x,y= (answser in m)

6. Two resistors, Ra = 7,500 ohms and Rb = 15,000 ohms, are connected in series. If a 120-volt source is applied to the combination, a) determine Ea and Eb when a 15,000-ohm resistance (in the form of a voltmeter) is first connected across resistor A and then across resistor B, b) determine Ea and Eb if one 15,000-ohm resistance (in the form of a voltmeter) is connected across A at the same time that another 15,000-ohm resistance is connected across B.