A 0.600 kg block is attached to a spring with spring constant 18.0 N/m . While the block is sitting at rest, a student hits it with a hammer and almost instantaneously gives it a speed of 40.0 cm/s . What is the block's speed at the point where x= 0.550 A?

Very short pulses of high-intensity laser beams are used to repair detached portions of the retina of the eye. The brief pulses of energy absorbed by the retina welds the detached portion back into place. In one such procedure, a laser beam has a wavelength of 810 nmand delivers 250 mW of power spread over a circular spot 510 μm in diameter. The vitreous humor (the transparent fluid that fills most of the eye) has an index of refraction of 1.34.

Part A

If the laser pulses are each 1.50 ms long, how much energy is delivered to the retina with each pulse?

Express your answer with the appropriate units.

Part B

What average pressure would the pulse of the laser beam exert at normal incidence on a surface in air if the beam is fully absorbed?

Express your answer with the appropriate units.

Part C

What are the wavelength of the laser light inside the vitreous humor of the eye?

Express your answer with the appropriate units.

Part D

What is the frequency of the laser light inside the vitreous humor of the eye?

Express your answer with the appropriate units.

Part E

What is the maximum value of the electric field in the laser beam?

Express your answer with the appropriate units.

Part F

What is the maximum value of the magnetic field in the laser beam?

A spy satellite is in circular orbit around Earth. It makes one revolution in 5.99 hours. How high above Earth's surface is the satellite?

: 10368477 m
11.[2pt]
What is the satellite's acceleration?

A point charge q1 = -4.00 nC is at the point x = 0.60 m, y = 0.80 m , and a second point charge q2 = +6.00 nC is at the point x = 0.60 m , y = 0.

A) Calculate the magnitude of the net electric field at the origin due to these two point charges

B) Calculate the direction of the net electric field at the origin due to these two point charges.

A small spring-loaded launcher is designed to fire steel ball bearings with masses of 0.24 kg . When setting the launcher, you compress the spring a distance of 12 cm . You then fire the launcher straight up and find that the projectiles reach a maximum height of 1.2 m above the point that they leave the launcher. You load another ball bearing, compress the spring a distance of 19 cm , and place it horizontally at the edge of a table that is 0.6 m tall. You fire the ball from the edge of the table. How far from the base of the table does it hit the ground?

The "reaction time" of the average automobile driver is about 0.7 s . (The reaction time is the interval between the perception of a signal to stop and the application of the brakes.) An automobile can slow down with an acceleration of 12.4 ft/s2 .

Part A

Compute the total distance covered in coming to a stop after a signal is observed from an initial velocity of 15.4 mi/h . (in a school zone)

Part B

Compute the total distance covered in coming to a stop after a signal is observed from an initial velocity of 56.0 mi/h .

A 0.420 kg iron horseshoe that is initially at 450°C is dropped into a bucket containing 19.7 kg of water at 22.6°C. What is the final equilibrium temperature (in °C)? Neglect any heat transfer to or from the surroundings. Do not enter units.

On the planet Newtonia, a simple pendulum having a bob with a mass of 1.35kg and a length of 187.0cm takes 1.42s , when released from rest, to swing through an angle of 12.0?, where it again has zero speed. The circumference of Newtonia is measured to be 5.15

A place-kicker must kick a football from a point 36.0 m (about 40 yards) from the goal. Half the crowd hopes the ball will clear the crossbar, which is 3.05 m high. When kicked, the ball leaves the ground with a speed of 20.2 m/s at an angle of 51.0° to the horizontal.

(a) By how much does the ball clear or fall short (vertically) of clearing the crossbar? (Enter a negative answer if it falls short.)

Find the two initial velocity components, and from them and the equations of motion, determine the time and height when the football has traveled the required distance measured along the ground. m

(b) Does the ball approach the crossbar (and cross above or beneath it) while still rising or while falling?

rising

or falling    

Consider the following questions and a student's response to each question (shown in italics). In each case, determine if the student's answer is true or false.

Explain the reasons that the distance curve has the shape it does.

The distance curve is an increasing curved line because the object is accelerating.

TrueFalse    

The velocity curve is an increasing straight line. What does this mean?

The velocity curve is a straight line because the object is moving with constant speed.

TrueFalse    

Calculate the slope of the velocity curve. Do you recognize what this is?

The slope of the velocity curve is the acceleration of the object and I calculated a slope of about 4.9 m/s².

TrueFalse    

The acceleration curve is a horizontal straight line. What does this mean?

The acceleration curve is a horizontal line because the acceleration of the object does not change with time.

TrueFalse

Q2. A ball is released from the top of a cliff; it hits the ground 3.5 seconds later. Assuming the ball is a free falling object, how many meters is the cliff above the ground below? (Use

g = 9.8 m/s².

Express your answer to one decimal point.)

Q3. The velocity vs. time curve of an object is an increasing straight line. You observe that when the time is 1 second, the velocity is equal to 4 m/s, and when the time is 4 seconds, the velocity is 28 m/s.What is the acceleration of the object? (Express your answer to one decimal point.)

Q4. What is the magnitude of the acceleration of a modified Atwood machine if the mass of the cart is 8 kg and the hanging mass is 10 kg? (Use

g = 9.8 m/s².

Express your answer to one decimal point.

Q5 In a completely frictionless Newton's Cradle toy, the change in speed of the balls coming in and those going out is zero. This is because the net force at the time of the collisions is equal to the weight of the number of balls interacting.

TrueFalse

A charge 5.05 nC is placed at the origin of anxy-coordinate system, and a charge -1.97 nC is placed on the positive x-axis at x = 3.99 cm . A third particle, of charge 6.03 nC is now placed at the point x = 3.99 cm , y = 3.00 cm .

(1)Find the x-component of the total force exerted on the third charge by the other two.

(2)Find the y-component of the total force exerted on the third charge by the other two.

(3)Find the magnitude of the total force acting on the third charge.

(4Find the direction of the total force acting on the third charge.

Possible Duplicate:
Black hole formation as seen by a distant observer

Given that matter can never cross the event horizon of a black hole (from an external observer point of view), if a black hole is "fed" with a large amount of matter then the new matter will eventually become extremely compressed, and presumably would be compressed below its Schwarzchild radius.

Would secondary black holes eventually form near the original black hole?

As an alternative one could also imagine that the combined mass of the original black hole and the new mass around the event horizon becomes contained within the Schwarzchild radius of both masses, and so a new event horizon forms, "swallowing" the new mass around the edge of the original black hole.

This mechanism would allow black holes to swallow mass in a finite time.
Would this contradict GR predictions?

Four masses are at the corners of a square of length ℓ = 20.0 cm and a fifth mass is at the center of the square. The masses are m₁ = 5.00 g, m₂ = 3.00 g, m₃ = 1.00 g, m₄ = 5.00 g, and m₅ = 1.50 g.

a-Draw the free body diagram for fifth mass.

b-Determine the net gravitational force on the fifth mass in unit vector notation.

Answer the following questions about one-dimensional motion.

1. Imagine a fox darting around in the woods for several hours. Can the displacement △xof the fox from his initial position ever be larger than the total distance d he traveled? Explain.
2. What is the difference between acceleration and velocity? Write a paragraph that would make sense to a 5th grader.
3. Give an example of a situation where an object has an upward velocity, but a downward acceleration.
4. What is the difference between average and instantaneous velocity? Make up an example involving a trip in a car that demonstrates your point.
5. If the position of an object is increasing linearly with time (i.e., △x is proportional to t), what can we say about its acceleration? Explain your thinking.
6. If the position of an object is increasing non-linearly with time (i.e., △x is not proportional to t), what can we say about its velocity? Explain your thinking.