1. Copyright - Adam Randall Electrostatics – Practice Problems Problem 1 Problem 1 – Lunar Athletes & Apparent Weight Problem 1 Problem 2 Problem 2 – Electric Field Safety Net Problem 2 Problem 3 Problem 3 – Long Distance Crater Jumping Problem 3 Problem 4 Problem 4 – Athletes Field Problem 4 Click on this icon to return to the this slide.

2. Copyright - Adam Randall B.Predict the strength of the electric force field needed to give the athlete an apparent weight on the moon equal to their weight on the Earth. A.If the athlete above wanted an apparent weight equal to their weight on the Earth, would their suit need an excess or deficiency of electrons? In the future, many Olympic athletes will train on the moon. The moons gravitational force field is nearly 1/6 th of the Earths. Special training facilities will be built to maintain variable strength / uniform electric force fields inside different training rooms. Athletes will wear electrically charged body suits designed to evenly distribute charge and the resulting electric force. The result will be a unique training environment able to create apparent weights ranging from 1/6 th mg to 2mg. q = 0.70C magnitude of charge on athletes suit m = 78 kg athletes mass + +++++ ____________ Problem 1 Problem 1 Problem 1 Problem 1

3. Copyright - Adam Randall Problem 2Problem 2Problem 2Problem 2 + ++ _ _ _ Photogate A. Predict the charge polarity of the athletes suit in order for the electric safety net to work. B. Predict the strength of the electric force field needed in order to save the athlete. A 72 kg Lunar athlete falls from rest from a 15 meter high platform wearing a body suit charged with 0.35 C. As a built in safety measure a photogate is placed 5.0 meters above the floor and measures the speed of the falling athlete. Instantly a uniform electric field is created to gently slow them down and decelerate them to rest on the surface of the floor. Coulombs Lunar Safety Net 5 m

4. Copyright - Adam Randall Consider a 60. kg athlete trying to jump a 1250 meter wide lunar crater shown below. Their initial velocity is 4.5 m/s at 45 degrees. If the electric field points up and has a strength of 25000 N/C, what in the minimum net charge the athlete must have on their body suit to jump the crater? Problem 3Problem 3Problem 3Problem 3

5. Copyright - Adam Randall Hint 3Hint 3Hint 3Hint 3 Decompose the initial velocity vector into components. Determine the time in flight from one side of the crater to the other. Determine the vertical acceleration using ΔY= 0 meters Use Newtons 2 nd Law to find the charge on jumper. VoVo V oy V ox Hints

6. Copyright - Adam Randall Imagine four electrically charged athletes standing on the vertices of a square 2 meters on a side. The two athletes on the top of the square carry -0.25 Coulombs of charge. The two athletes on the bottom of the square carry +0.25 Coulombs of charge. Proble m 4 A.Determine the electric field (vector) at the exact center of the square. B.Determine the electric force (vector) on a 0.1 gram water drop with 10,000 extra electrons on it, at the center of the square. C.Could you use the standard equations of kinematics to predict the motion of the water drop through space and time? 2 meters