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?

What quantity must be small to ensure the validity of the Fresnel approximation (Use the second-order term of the Taylor series expansion)?

a pilot has his small airplane heading due north at 50 km/h. after two hours of flight he finds himself 40 km east and 70 km north of his starting point. find the velocity of the crosswind that is driving the plane off-course?

A 500 Kg bloack of ice at -25 degrees celsuis is placed in just enough liquid water at 100 degrees celsius to completely melt it.

A) what was the mass of the hot water?

B) what was the entropy change of the ice?

C) what was the entropy change of the hot water ?

D) what was the entroyp change of the universe ?

E) what would the finaly temperature have been if intially the liquid water was instead 100 degree celsius water vapor ?

F) for part E what waould be the entropy chnage of

i) ice ? ii) water vapor ? iii) universe ?

Hi! I have some questions I'd like to discuss regarding an experiment with the pendulum

I will have a laboratory class in which I will have to measure the period of oscillation of the swinging pendulum using an electronic stopwatch.

what method could I use to obtain the period of a physical pendulum using a stopwatch, taking care to minimise any uncertainties?

Can you help me to go through this questions?

Should you start the stopwatch at the same time as you set the pendulum swinging, or would it be better to start the pendulum swinging and begin timing later?

Will you measure the time for just one “to-and-fro” swing (i.e. one period), or the time for multiple swings and then divide the time by the number of swings to get the period?

How many measurements will you make at a particular pendulum length? Would it be better to take the average of several measurements?

What angle will you be using? Why?

What is the uncertainty in the length of the pendulum? Is it limited by the precision

of your equipment or something else?

What is the minimum length that you will be using? Why?

Derive The Dirac Equation.

A balloon is filled up completely with helium gas and left in a room with a controlled temperature of 230C. After two days of being in the same room, the balloon was found to have shrunk to half its filled-up size. However, there was no leakage of helium gas from the balloon during the two days. Explain what happened to the pressure inside the balloon due to the change in the size of the balloon. ?  Use Boyle's Law to explain your answer.