Explain the following natural events in terms of the laws of physics that you have learned in this class. Include figures if necessary. Answer any two.

How does a bird fly?

If you keep boiled egg inside refrigerator, it becomes difficult to take the shell off. But if you keep it warm water for a minute or so it becomes very easy. Why?

Why inside swimming pool we feel very light weight?

Mention all the laws of physics applied in these processes.

Explain the following natural events in terms of the laws of physics that you have learned in this class. Include figures if necessary. Answer any two.

How does a bird fly?

If you keep boiled egg inside refrigerator, it becomes difficult to take the shell off. But if you keep it warm water for a minute or so it becomes very easy. Why?

Why inside swimming pool we feel very light weight?

Mention all the laws of physics applied in these processes.

(a) Using Kirchhoff’s laws, derive an equation for the voltages, V1 and V2, across two resistors, R1 and R2, in series connected to a voltage supply V .

(b) Using Kirchhoff’s laws, derive an equation for the voltages across two resistors R1 and R2 in parallel connected to a voltage supply V .

1- relate characteristics of semiconductor basic mechanism of electrical conduction

2- determine important parameters of semiconductor

3- describe operation principle of semiconductor devices

4- demonstrate the understanding of intrinsic-extrinsic semiconductor characteristic`.

A picture window has dimensions of 1.40 m

A 120-pF capacitor and a 480-pF capacitor are both charged to 3.10 kV. They are then disconnected from the voltage source and are connected together, positive plate to negative plate and negative plate to positive plate.

(a) Find the resulting potential difference across each capacitor.

(b) Find the energy lost when the connections are made.
µJ

A 45 kg figure skater is spinning on the toes of her skates at 0.50 rev/s . Her arms are outstretched as far as they will go. In this orientation, the skater can be modeled as a cylindrical torso (40 kg , 20 cm average diameter, 160 cm tall) plus two rod-like arms (2.5 kg each, 62 cm long) attached to the outside of the torso. The skater then raises her arms straight above her head, where she appears to be a 45 kg, 20-cm-diameter, 200-cm-tall cylinder. Part A What is her new rotation frequency, in revolutions per second? Express your answer to two significant figures and include the appropriate units.

What is her new rotation frequency, in revolutions per second?

A spherical bowling ball with mass m = 3.3 kg and radius R = 0.11 m is thrown down the lane with an initial speed of v = 8.9 m/s. The coefficient of kinetic friction between the sliding ball and the ground is ? = 0.28. Once the ball begins to roll without slipping it moves with a constant velocity down the lane.

What is the magnitude of the angular acceleration of the bowling ball as it slides down the lane?

What is magnitude of the linear acceleration of the bowling ball as it slides down the lane?

How long does it take the bowling ball to begin rolling without slipping?

How far does the bowling ball slide before it begins to roll without slipping?

What is the magnitude of the final velocity?

Current passes through a solution of sodium chloride. In 1.00 second, 2.68

16. Briefly explain why each of the following statements is likely to be either true or false, giving reason(s) based on the concepts discussed in class. Ignore friction.

1. a) A sports utility vehicle (SUV) hits a stationary motorcycle. The motorcycle experiences a greater force than the SUV does.

2. b) A semitrailer truck crashes through a wall. Since the wall collapses, the wall sustains a greater force than the truck does.

3. c) Sam (18 years old) and his sister Janice (7 years old) go ice skating. They push off against each other and fly apart. Janice flies off with the greater acceleration.

William Tell is said to have shot an apple off his son’s head with an arrow. If the arrow was shot with an initial speed of 50.0 m/s and the boy was 28.0 m away, at what launch angle above the horizontal did Bill aim the arrow? (Assume that the arrow and apple are initially at the same height above the ground. Hint: sin2θ = 2sinθcosθ)

Akao

2. Aa consequence of a fall-out, two radioactive beta emitting isotopes are released. Tritium, with a physical half-life time of 12 years and an average beta energy of 6keV, and¹³⁷Cs, with 30 years half-life time and an electron with average energy of 170 keV (we neglect the also emitted high energy y-ray here)

   1. a) A human of 100Kg ingests 107 Bq of tritium and 10³ Bq of ¹³⁷Cs. No additional activity is taken in afterwards. What is the whole body dose from each isotope the human receives over the first 1 day? Assume here that all the activity stays constant in the body over the day.

   2. b) One year after the incident, what is the dose over the year from the given ingested activity from each isotope? Assume tritium has 10 days and Caesium15 years of biological half-life time in the human body.

The single most important use of the element gold is for wires that join integrated circuits to the conducting pads that then connect microelectronic chips with external circuitry. A typical application uses gold wires 1.0 milmil (0.001 inch) in diameter and 45 milmil long. Although the current under normal conditions is much less, such a wire will fuse (that is, melt and interrupt the current) when the current exceeds some 660 mAmA.

A) Find the current density in the wire when this maximum current is flowing.

B) Find the electric field in the wire when this maximum current is flowing.

C) Find the voltage between the ends of the wire when this maximum current is flowing.

Charge is added to a spherical conductor of radius 20.0 cm.

(a) If the maximum electrical field the air surrounding the sphere can sustain without the molecules being ionized is 3.00 × 10⁶ V/m, what is the maximum charge that can be placed on the sphere?

Let the charge placed on the sphere be 5.00 μC.

(b) What is the potential at the surface of the sphere?

(c) What is the potential at a point located 10.0 cm from the center of the sphere?

(d) What is the potential at a point located outside the sphere at a distance of 5.00 cm from the surface of the sphere?