1. Describe a scenario where two objects are electrically attracted to one another, but one of the objects is neutral in charge

2. What would happen if the force of gravity was stronger than the electrical force between two charges in space?

A bat flying at 4.80 m/s is chasing an insect flying in the same direction. The bat emits a 40.0-kHz chirp and receives back an echo at 40.4 kHz. (Take the speed of sound in air to be 340 m/s.)

What is speed of insect (m/s)

Problem 9: Suppose that a 115 kg football player running at 5.5 m/s catches a 0.47 kg ball moving at a speed of 25.5 m/s with his feet off the ground, while both of them are moving horizontally.

Part (a) Calculate the final speed of the player, in meters per second, if the ball and player are initially moving in the same direction. Numeric : A numeric value is expected and not an expression. vf,1 = __________________________________________

Part (b) Calculate the change in kinetic energy of the system, in joules, after the player catches the ball. Numeric : A numeric value is expected and not an expression. ΔKE1 = __________________________________________

Part (c) Calculate the final speed of the player, in meters per second, if the ball and player are initially moving in opposite directions. Numeric : A numeric value is expected and not an expression. vf,2 = __________________________________________

Part (d) Calculate the change in kinetic energy of the system, in joules, in this case. Numeric : A numeric value is expected and not an expression. ΔKE2 = __________________________________________

A sheet of glass (n=1.50) is coated with a 500 nm -thick layer of oil (n=1.42).

A. For what visible wavelengths of light do the reflected waves interfere constructively? The range of wavelength of visible light is from 380 nm to 750 nm.

B. For what visible wavelengths of light do the reflected waves interfere destructively?

C. What is the color of reflected light?

D. What is the color of transmitted light?

A rock is suspended by a light string. When the rock is in air, the tension in the string is 52.9 N . When the rock is totally immersed in water, the tension is 32.6 N . When the rock is totally immersed in an unknown liquid, the tension is 14.4 N .

What is the density of the unknown liquid?

Ohm’s Law in terms of the applied potential. But we can re-express the potential as the integral of the electric field along some path. We can also re-express electrical resistance in terms of conductivity, length, and cross-section. Use these relationships to write Ohm’s Law in terms of the electric field and the current density.  What physical parameter does a linear fit to the slope of the resistor current graph represent? Why is a similar graphical analysis of the diode current not appropriate?

A series ac circuit consists of a voltage source of frequency f = 60 Hz and source voltage amplitude 345 volts, a resistor of resistance R = 255 Ω, a capacitor of capacitance C = 6.2×10−6F, and an inductor of inductance L.

(a) What must be the value of L for the phase angle Φ to be zero?

(b) When L has the value calculated in (a), what is the current amplitude in the circuit?

A wagon is rolling forward on level ground. Friction is negligible. The person sitting in the wagon is holding a rock. The total mass of the wagon, rider, and rock is 98.9 kg. The mass of the rock is 0.291 kg. Initially the wagon is rolling forward at a speed of 0.490 m/s. Then the person throws the rock with a speed of 16.1 m/s. Both speeds are relative to the ground. Find the speed of the wagon after the rock is thrown (a) directly forward in one case and (b) directly backward in another.

A copper collar is to fit tightly about a steel shaft whose diameter is 7.0000 cm at 20° C. The inside diameter of the copper collar at that temperature is 6.9760 cm. After the collar is heated and fitted about the steel shaft, it begins to cool. What is the tensile stress in the copper collar when its temperature returns to 20° C?

____________________N/m2

A vertical spring (ignore its mass), whose spring constant is 825 N/m , is attached to a table and is compressed down by 0.160 m.

A)What upward speed can it give to a 0.360-kg ball when released? Express your answer to three significant figures and include the appropriate units.

B) How high above its original position (spring compressed) will the ball fly? Express your answer to three significant figures and include the appropriate units.

A 123 turn circular coil of radius 2.27 cm is immersed in a uniform magnetic field that is perpendicular to the plane of the coil. Over an interval of 0.167 s , the magnetic field strength increases from 54.5 mT to 94.1 mT . Find the magnitude of the average emf avg induced in the coil during this time interval, in millivolts.

A 45.0-g object connected to a spring with a force constant of 50.0 N/m oscillates with an amplitude of 7.00 cm on a frictionless, horizontal surface.

(a) Find the total energy of the system.

(b) Find the speed of the object when its position is 1.30 cm. (Let 0 cm be the position of equilibrium.)

(c) Find the kinetic energy when its position is 3.50 cm.

(d) Find the potential energy when its position is 3.50 cm.

A railroad car of mass 3.10 ✕ 10^4 kg moving at 3.50 m/s collides and couples with two coupled railroad cars, each of the same mass as the single car and moving in the same direction at 1.20 m/s.

(a) What is the speed of the three coupled cars after the collision?

__m/s

(b) How much kinetic energy is lost in the collision?

__J

The Photoelectric Effect Lab 10

Prelab Questions : Predictions

1. If the light shining on the metal becomes brighter, will the kinetic energy of the emitted electrons increase?

2. If the light shining on the metal becomes brighter, will the number of electrons being emitted per second (the photo-current) increase?

3. If the frequency of the light shining on the metal is increased, will the number of electrons being emitted per second (the photo-current) increase?

4. If the frequency of the light shining on the metal is increased, will the kinetic energy of electrons being emitted increase?

5. Will all colors (frequencies) of light cause electrons to be emitted by the metal? What is the condition on wavelength for Potassium that light should cause electrons to be ejected?

5. If light with the same frequency and same power shines on two different metals with different work functions, will both metals emit electrons?
   1. Will these electrons have the same kinetic energy?
   2. Will the photo-current be larger for the metal with the smaller work function?

(1) Parasaurolophus was a dinosaur whose distinguishing feature was a hollow crest on the head. The 1.2m long hollow tube in the crest had connections to the nose and throat, leading some investigators to hypothesize that the tube was a resonant chamber for vocalization. (Figure 1)

If you model the tube as an open-closed system, what are the first three resonant frequencies? (Use 350 m/s for the speed of sound.)

Enter your answers using two significant figures in ascending order separated by commas.

(2) Tendons are, essentially, elastic cords stretched between two fixed ends; as such, they can support standing waves. These resonances can be undesirable. The Achilles tendon connects the heel with a muscle in the calf. A woman has a 20-cm-long tendon with a cross-section area of 120mm2. The density of tendon tissue is 1100 kg/m3.

For a reasonable tension of 600N , what will be the fundamental resonant frequency of her Achilles tendon?

Express your answer to two significant figures and include the appropriate units.