Refraction of Material, DC Motor Current, Defibrillator & Speed

1. A light ray in material 1 goes into material 2. The angle of incidence in material 1 is 40.0o and the angle of refraction in material 2 is 31.0o. If the index of refraction of material 1 is 1.60, what is the index of refraction of material 2?

2. A dc motor has coils with a resistance of 16 and is connected to an emf of 120.0 V. When the motor operates at full speed, the back emf is 72 V. What is the current in the motor when it first starts up?

3. A defibrillator is used to restart a person's heart after it stops beating. Energy is delivered to the heart by discharging a capacitor through the body tissues near the heart. If the capacitance of the defibrillator is 9 ìF and the energy delivered is to be 300 J, to what potential difference must the capacitor be charged?

4. Why is the speed of sound in solids generally much faster than the speed of sound in air? What happens when a sound wave goes from the air in a room and encounters a brick wall?

5. A curve in a stretch of highway has radius R. The road is unbanked. The coefficient of static friction between the tires and road is µs. What is the fastest speed that a car can safely travel around the curve?

6. In the physics laboratory, a glider is released from rest on a frictionless air track inclined at an angle. If the glider has gained a speed of 25.0 cm/s in travelling 50 cm from the starting point, what is the angle of inclination of the track?

7. Two children ride on a Merry-go-round. One is 2 m from the axis of rotation and the other is 4 m from it. Which child has the larger;
I. linear speed
II. acceleration
III. angular speed and
IV. angular displacement?

8. Household wiring is made with ____?