Answers

This page will be used to post answers to homework assignments. All answers are subject to rounding errors but should be close.

B - Atoms and Charge

1. v = 2.18 x 10⁶ m/s
2. q = -1.68 x 10^-11 C

B - Pressure and Buoyancy

1. F_Net = 2,673,000 N down -> SINK; ∆V = 272 m³
2. V = will around 0.05 m³ to 0.1 m³; Around 20% of 1st answer should be out of water
3. V = will around 525 m³ to 675 m³

B - Thermo and Fluids

1. P = 20,156 W
2. r_{center of Earth} = 0.00158 m; r_{Mt. Everest} = 0.326 m

B - Waves

1. 80 Hz: λ_air = 4.29 m; λ_water = 18.66 m; 1 kHz: λ_air = 0.343 m; λ_water = 1.493 m
2. Lowest: 7,500 Hz; Second Lowest: 15,000 Hz
3. Will vary among topics. Some do not lend themselves well to this question (optical illusions for instance). Do your best to describe your topic well while also demonstrating an understanding of waves.

B - Periodic Motion

1. With a period of T = 2 s -> L = 0.993 m
2. T = 10.22 s; f = 0.098 Hz; 352.25 pushes in an hour
3. Drawing would look like waves; λ_clock = 2.8 m; λ_Foucault = 14.3 m

Thermodynamics Homework

1. The energy goes to heat. The tires should get hot.
2. ∆T = 1.65 K
3. ∆T for pan = -93 K; Original temp = 104 degrees C

Friction and Inclined Planes

1. F_f = 7.62 N; F_Net = 8.27 N
2. V_f = 18.1 m/s
3. µ = 0.53

Friction Homework

1. µ = 0.31
2. F_Net = 0.88 N u; a = 0.29 m/s² 
3. V_o = 17.64 m/s

Free Body Diagram Worksheet

1. F_Net = 6000 N forward; a = 8 m/s²
2. F_Net = 2000 N up stream; a = 0.2 m/s² 
3. F_Net = 735 N down; a = -9.8 m/s² 
4. F_Net = 7.2 N a = 0.36 m/s² 

Football Problem

It is the last play of a football game and the quarterback needs to hit his fastest wide receiver in stride so that he can score the game winning touchdown. The quarterback, who wears number 34, is 6 ft 3 in tall and had a cheeseburger for lunch. To account for air resistance, the height of the linemen, and the way that his should pads restrict his movement he releases his furthest throws so that the ball is traveling at an angle of 30^o above the horizon. The wide receiver is fast, he runs a 40 m sprint in 4.21 s. He also has the same reach at the quarterback. One time the wide receiver ate a popsicle. The quarterback can throw the football at 57.2 mph. He has been practicing over and over again on the timing of his passes. He has gotten it down to exactly three seconds from the snap to when he releases the ball. If he throws the ball as hard as he can on a Hail Mary will the receiver be fast enough to get to where the ball lands in time? If the receiver is too slow how far away from the ball will he be? What would be the perfect amount of time for the quarterback to wait after the snap to throw the ball?

∆x_ball = 59.63 m 
∆x_WR = 53.68 m  

∆x_behind = 5.95 m

t_snap = 3.63 s

Vertical Motion Homework

1. ∆y = -29.86 m   ---> man is on the 10th floor
   ∆y = -9.02 m   ---> couch started 3 floors above man, 13th floor.
2. t = 6.53 s
   ∆y_max = 52.23 m
3. ∆x = 32.5 m

Motion and Acceleration Homework

1. t = 530 s
   v = 20.75 m/s
2. a = 11.3 m/s²
   v_f = 95.17 m/s
3. t = 4.3 s
   
   ∆x = 79.55 m