(2a) A 4750.0 kg open train car is rolling on frictionless rails at 24.3 m/s when it starts pouring rain. A few minutes later, the car's speed is 18.0 m/s. What mass of water has collected in the car?

(2b) Two 485.0 g blocks of wood are 2.65 m apart on a frictionless table. A 23.1 g bullet is fired at 384.5 m/s toward the blocks. It passes all the way through the first block, then embeds itself in the second block. The speed of the first block immediately afterward is 1.07 m/s. What is the speed of the second block after the bullet stops?

(2c) A 2.67 kg sphere makes a perfectly inelastic collision with a second sphere that is initially at rest. The composite system moves with a speed equal to one third the original speed of the 2.67 kg sphere. What is the mass of the second sphere?

Explain what is interference, refraction and reflection in waves.

Intro to Astronomy:

Please CONCISELY answer these questions, thank you!

1.) Suppose the amount of mass in a black hole doubles, does the event horizon change? If so, does it grow, shrink, or stay the same size? And what physical force limits the growth of supermassive black holes?

2.) Assume that the distance from one edge of the Milky Way Galaxy to the other is 1 cm, with this same scale how far away is the Andromeda Galaxy? Why do astronomers believe that gravitation in the universe is dominated by dark matter?

3.)Consider a stellar black hole that used to be a 100 solar mass main sequence star and a planet orbiting around it at 10 AU. From the planet's position (pretend it survived the Type 2 supernova), was the star or black hole a stronger gravitational object?

Of the fundamental forces, the text claims that “gravity dominates on very large scales.” However, both the gravitational force and the electric force decrease in proportion to the inverse squared distance. Explain why the electric force isn't as strong as the gravitational force at very large distances.

. (a) Draw the basic setup for quantum key distribution.

(b) Explain the “intercept-resend” attack that Eve can attempt (draw a simple figure).

(c) Explain how this attack is thwarted by the quantum key distribution protocol. How can Eve’s attack be detected?

(d) What does the security of quantum key distribution rely on fundamentally?

(part 1 of 2)

An electric car is designed to run on a bank of batteries with a total potential difference of 29 V and a total energy storage of 2.2×107 J. If the electric motor draws 6.8 kW, what is the current delivered to the motor? Answer in units of A.

(part 2 of 2) If the electric motor draws 6.8 kW as the car moves at a steady speed of 47.0 m/s, how far will the car travel before it is “out of juice”? Answer in units of m.

You have set up an experiment where two Stern-Gerlach analyzers sequentially measure spin along the z-axis. The first analyzer allows particles with spin up along z to pass. The second analyzer allows particles with spin down along z to pass. Between the two analyzers is a magnetic field aligned along +x. Your experiment sends identical spin-1/2 particles at speed v along the y-axis through the analyzers, which are separated by a distance Δy. What is the smallest distance Δy that will transmit 50% of the particles passed through the first analyzer through the second analyzer?

Show that if qd≫1 the probability for tunneling through a potential barrier of width d is proportional to e^(-2qd). Plot this function and explain the implications.

While vacationing in the mountains you do some hiking. In the morning, your displacement is S⃗ morning= (2200 m , east) + (4000 m north) + (200 m , vertical). After lunch, your displacement is S⃗ afternoon= (1600 m , west) + (2900 m , north) - (300 m , vertical).

Part A

At the end of the hike, how much higher or lower are you compared to your starting point?

Express your answer with the appropriate units

Part B

What is the magnitude of your net displacement for the day?

Express your answer with the appropriate units.

7. The University Skydiving Club has asked you to plan a stunt for an air show. In this stunt, two skydivers will step out of opposite sides of a stationary hotair balloon 1500 meters above the ground. The second skydiver will leave the balloon 20 seconds after the first skydiver but you want them both to land on the ground at the same time. The show is planned for a day with no wind so assume that all motion isvertical. To get a rough idea of the situation, assume that a skydiver will fall with a constant acceleration of 9.80 m/s2before the parachute opens. As soon as the parachute is opened, the skydiver falls with a constant velocity of 3.2 m/s. If the first skydiver waits 3 seconds after stepping out of the balloon before opening her parachute, how long must the second skydiver wait after leaving the balloon before opening his parachute?

A 65kg skater travelling northward at 3.8m/s accidentally collides with a 75kg skater travelling west at 2.4m/s. They hold on to each other while attempting to regain balance and continue moving in that direction after the collision. What total speed and direction (find angle) do the skaters move together after the collision?

The drive propeller of a ship starts from rest and accelerates at 2.99 x 10-3 rad/s2 for 2.86 x 103 s. For the next 1.90 x 103 s the propeller rotates at a constant angular speed. Then it decelerates at 2.61 x 10-3 rad/s2 until it slows (without reversing direction) to an angular speed of 2.31 rad/s. Find the total angular displacement of the propeller.