As a city planner, you receive complaints from local residents about the safety of nearby roads and streets. One complaint concerns a stop sign at the corner of Pine Street and 1st Street. Residents complain that the speed limit in the area (55 mph) is too high to allow vehicles to stop in time. Under normal conditions this is not a problem, but when fog rolls in visibility can reduce to only 155 feet. Since fog is a common occurrence in this region, you decide to investigate. The state highway department states that the effective coefficient of friction between a rolling wheel and asphalt ranges between 0.536 and 0.599, whereas the effective coefficient of friction between a skidding (locked) wheel and asphalt ranges between 0.350 and 0.480. Vehicles of all types travel on the road, from small VW bugs weighing 1150 lb to large trucks weighing 7440 lb. Considering that some drivers will brake properly when slowing down and others will skid to stop, calculate the miminim and maximum braking distance needed to ensure that all vehicles traveling at the posted speed limit can stop before reaching the intersection.

A uniform ladder stands on a rough floor and rests against a frictionless wall as shown in the figure. 2 58 1 Since the floor is rough, it exerts both a normal force N1 and a frictional force f1 on the ladder. However, since the wall is frictionless, it exerts only a normal force N2 on the ladder. The ladder has a length of L = 4.5 m, a weight of WL = 63.5 N, and rests against the wall a distance d = 3.75 m above the floor. If a person with a mass of m = 90 kg is standing on the ladder, determine the following.

(a) the forces exerted on the ladder when the person is halfway up the ladder (Enter the magnitude only.)

N1 = ____ N

N2 = ____ N

f1 = ____ N

(b) the forces exerted on the ladder when the person is three-fourths of the way up the ladder (Enter the magnitude only.)

N1 = ____ N

N2 = ____ N

f1 = ____ N

An green hoop with mass m_h = 2.8 kg and radius R_h = 0.12 m hangs from a string that goes over a blue solid disk pulley with mass m_d = 1.9 kg and radius R_d = 0.09 m. The other end of the string is attached to a massless axel through the center of an orange sphere on a flat horizontal surface that rolls without slipping and has mass m_s = 3.8 kg and radius R_s= 0.22 m. The system is released from rest.

What is magnitude of the linear acceleration of the hoop?

What is magnitude of the linear acceleration of the sphere? '

What is the magnitude of the angular acceleration of the disk pulley?

What is the magnitude of the angular acceleration of the sphere?

What is the tension in the string between the sphere and disk pulley?

What is the tension in the string between the hoop and disk pulley?

The green hoop falls a distance d = 1.69 m. (After being released from rest.) How much time does the hoop take to fall 1.69 m?

What is the magnitude of the velocity of the green hoop after it has dropped 1.69 m?

What is the magnitude of the final angular speed of the orange sphere (after the green hoop has fallen the 1.69 m)?

In the figure, a conducting rod of length L = 29.0 cm moves in a magnetic field B⃗ of magnitude 0.390 T directed into the plane of the figure. The rod moves with speed v = 6.00 m/s in the direction shown.

When the charges in the rod are in equilibrium, what is the magnitude E of the electric field within the rod?

What is the magnitude Vba of the potential difference between the ends of the rod?

What is the magnitude E of the motional emf induced in the rod?

Assume that the firework has a mass of m_0 = 0.30~\text{kg}m​0​​=0.30 kg and is launched from a cannon at an angle of \theta_0 = 41.8^\circθ​0​​=41.8​∘​​ with an initial velocity of | v_0 | = 20~\text{m/s}∣v​0​​∣=20 m/s. Just as the firework reaches its hight point in its trajectory, it explodes into two pieces. Immediately after the explosion, the first piece, with a mass of m_1 = 0.2~\text{kg}m​1​​=0.2 kg flies off at an angle \theta_1 = 150^\circθ​1​​=150​∘​​ relative to the positive (forward) horizontal axis at a velocity of | v_1 | = 5~\text{m/s}∣v​1​​∣=5 m/s relative to the ground. Calculate the trajectory angle, \theta_2θ​2​​ of the second piece immediately after the explosion. Assume the second piece has a mass of m_2 = 0.1~\text{kg}m​2​​=0.1 kg, neglect the effect of air resistance, and report your result as an angle relative to the positive (forward) horizontal axis.

An ice cube whose mass is 50 g is taken from a freezer at a temperature of -10C and then dropped into a cup of water at 0C. If no heat is gained or lost from the outside, how much water will freeze onto the cup?

The tires of a car make 77 revolutions as the car reduces its speed uniformly from 92.0 km/h to 60.0 km/h. The tires have a diameter of 0.84 m.

1. What was the angular acceleration of the tires?

2. If the car continues to decelerate at this rate, how much more time is required for it to stop?

3. If the car continues to decelerate at this rate, how far does it go? Find the total distance.

Consider an electron in a hydrogen atom in the n=2,l=0 state. At what radius ( in units of a0) is the electron most likely to be found?

A particle of mass 4.00 kg is attached to a spring with a force constant of 300 N/m. It is oscillating on a horizontal frictionless surface with an amplitude of 5.00 m. A 9.00 kg object is dropped vertically on top of the 4.00 kg object as it passes through its equilibrium point. The two objects stick together.

a) By how much does the amplitude of the vibrating system change as a result of collision?

b) By how much does the period change?

c) By how much does the energy change?

What are some threshold concepts in Electricity and Magnetism Physics? Use the characteristics of threshold concepts to support your reasoning.

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The idea of using the sun’s energy was thought of the late 1870 when two American scienists became interested in the work of an electrican named willouhby smith who was testing underwater telegraph lines for faults using a material called selenium. Smith realized that electricity travelled through selenium well when it was in light, but it didn’t in the absence of light. It was not long before the scientists discovered that the sun’s energy generates a flow of electricity in selenium. It wasn’t until decade later that Charles Fritts invented the world’s first ever photovoltaic cell. He did this by putting a layer of selenium onto a metal plane and covering it with pieces of gold that had been beaten into thin sheet. Under the light this cell made even more electricity than had been seen with just selenium but not enough to be useful. At the time, photovoltaic technology was contending with other further developed technologies such as hydroelectricity and steam driven generators. Upon hearing of the developments in the field, Albert Einstein committed his studies to understanding the relationship between light and electricity. Building on the work of Plank, Einstein argued that light was actually made of tiny packets of energy that move likes waves. He referred to these ‘’energy packets’’ as photons. He later argued the energy of these photons is wavelength dependent, so the photons at visible wavelengths are more energetic than those of infared.

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It has become clear that at this point sustainability is the most important aspect of energy production. Perhaps the most accessible form of renewable energy for the everyday New Yorker at this solar energy. Due to the architectural setup it is difficult for New York citizen to harness energy from a windmill or even a hydro-dam. In more and more NY neighborhoods companies are installing solar panels on the roofs of building in order to store and use the sun energy

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The air pressure inside the tube of a car tire is 353 kPa at a temperature of 14.0 °C. What is the pressure of the air, if the temperature of the tire increases to 63.0 °C? Assume that the volume of the tube doesn't change.

What is the air pressure inside the tube, if the volume of the tube is not constant, but it increases from 21.0 l to 21.9 l during the warming process described above?

Objects with masses of 140 kg and a 440 kg are separated by 0.500 m.

(a) Find the net gravitational force exerted by these objects on a 43.0-kg object placed midway between them.

Magnitude:

(b) At what position (other than infinitely remote ones) can the 43.0-kg object be placed so as to experience a net force of zero?
   m from the 440-kg mass

(a) Estimate the terminal speed of a wooden sphere (density 0.790 g/cm3) falling through air, if its radius is 7.50 cm and its drag coefficient is 0.500. (The density of air is 1.20 kg/m3.)

[ ] m/s

(b) From what height would a freely falling object reach this speed in the absence of air resistance?