If the coefficient of kinetic friction is 0.2, what friction of the total mechanical energy is lost due to frictional forces?

A box of mass 18.0 kg sits at rest on a horizontal surface. The coefficient of kinetic friction between the surface and the box is 0.300. The box is initially at rest, and then a constant force of magnitude FF and direction 39.0 ∘∘ below the horizontal is applied to the box; the box slides along the surface.

A. What is F if the box has a speed of 6.00 m/s after traveling a distance of 8.00 mm? Express your answer with the appropriate units.

B. What is F_B if the surface is frictionless and all the other quantities are the same? Express your answer with the appropriate units.

C. What is F_C if all the quantities are the same as in part A but the force applied to the box is horizontal? Express your answer with the appropriate units.

Superhero physics: a) Choose a height between 1.00 miles and 3.00 miles. How fast would a superhero have to throw a ball straight upwards in order for it to rise this high? Give your answer in both m/s and mph. Assume air resistance is negligible, since at these speeds that's as believable as superheroes are. b) Choose a time between 1.00 minutes and 3.00 minutes. How fast would a superhero have to throw a ball straight upwards in order for it to spend this much time in the air (that is, for it to take that much time to return to their hand)? Give your answer in both m/s and mph. Same assumption. c) Without resorting to further calculations, which of these two balls will be in the air longer? Explain your reasoning, explicitly citing evidence. d) Choose one case, (a) or (b), and calculate the time required for the ball to rise halfway to its highest point, and the time to rise from there to the highest point. Check: see next question. e) Why does it take less time to rise halfway to the highest point than to rise the rest of the way?

Particle A and particle B are held together with a compressed spring between them. When they are released, the spring pushes them apart and they then fly off in opposite directions, free of the spring. The mass of A is 2.00 times the mass of B, and the energy stored in the spring was 50 J. Assume that the spring has negligible mass and that all its stored energy is transferred to the particles. Once that transfer is complete, what are the kinetic energies of (a) particle A and (b) particle B?

How are conversion electrons formed? List all the differences between an internal conversion process and beta decay?

A person with mass m=80 kg is training for pushups. Assume that the distance between the shoulders and the feet is 1.5 m, and the center of mass is at 1 m from the feet. First, he is trying to do a normal pushup. Assuming only vertical forces, what is the force on the arms?After that proved to be too difficult, he tries a modified version, where his arms are on the kitchen counter instead (~92 cm from the ground), which causes his body to form a 450 angle with the ground. What is the force on the arms, and what happens as the person expands their arms?

A small boat with a speed of 23km/h relative to the water is sailing in a sea which has a speed of 15 km/h relative to the shore in a direction E 16 N. What direction is the boat heading (relative to the water) if it is going in a direction N 32.7 E (relative to the shore)?
Hint: Suggested steps: Interpret the situation in terms of the relative velocity equation, indicating the meaning of all the subscripts. Draw a diagram roughly to scale, including all of the known information and using the parallelogram rule, on the coordinate system below. Solve for unknowns using geometry and sine and cosine laws.

A charge of -3.50 nCnC is placed at the origin of an xy-coordinate system, and a charge of 1.90 nCnC is placed on the yy axis at yy = 3.65 cmcm .

Part A: If a third charge, of 5.00 nCnC , is now placed at the point xx = 2.75 cmcm , yy = 3.65 cmcm find the xx and yy components of the total force exerted on this charge by the other two charges.

Part B: Find the magnitude of this force.

Part C: Find the direction of this force.

PLEASE ACTUALLY DO IT OUT! I TRIED TO DO THE BOTTOM ANSWERS AND KEPT GETTING WRONG FOR LAST TWO.

The heating coils in a hair dryer are 0.800 cm in diameter, have a combined length of 1.00 m, and a total of 375 turns.

(a) What is their total self-inductance assuming they act like a single solenoid?
H
(b) How much energy is stored in them when 11.5 A flows?
J
(c) What average emf opposes shutting them off if this is done in 4.17 ms (one-fourth of a cycle for 60 Hz AC)?
mV

Newton's 2nd law says that when a larger force is applied to an object of mass m, the object will experience a larger acceleration. At the same time, you've learned that all objects experience the same acceleration in a free fall, even if their weights (the forces of gravity acting on them) are different. That sounds like a contradiction: on one hand, from the Newton's 2nd law, a larger force means larger acceleration, on the other hand when applied to motion under gravity - a larger weight (force) means the same acceleration for all objects. How do you reconcile these statements? Why isn't it a contradiction? Does gravity violate the Newton's second law or is there another explanation. Be as thorough and clear in your explanation as possible.

A student runs an experiment with two carts on a low-friction track. As measured in the Earth reference frame, cart 1 (m = 0.48 kg ) moves from left to right at 1.0 m/s as the student walks along next to it at the same velocity. Let the +x direction be to the right.

a) What velocity v⃗ E2,i in the Earth reference frame must cart 2 (m = 0.16 kg ) have before the collision if, in the student's reference frame, cart 2 comes to rest right after the collision and cart 1 travels from right to left at 0.33 m/s?

b) What does the student measure for the momentum of the two-cart system?

c) What does a person standing in the Earth reference frame measure for the momentum of each cart before the collision?

At a particular location in your house, three appliances make sound intensity levels of 73.2 dB, 76.1 dB, and 69.2 dB individually. What is the sound intensity level at that location when they are all running at the same time?

A watermelon seed has the following coordinates: x = -6.4 m, y = 5.0 m, and z = 0 m. Find its position vector as (a) a magnitude and (b) an angle relative to the positive direction of the x axis. If the seed is moved to the xyz coordinates (3.0 m, 0 m, 0 m), what is its displacement as (c) a magnitude and (d) an angle relative to the positive direction of the x axis? Put the angles in the range (-180°, 180°].

A long, straight, copper wire with a circular cross-sectional area of
2.1 mm2
carries a current of 22 A. The resistivity of the material is 2.00 10-8?

How did Galileo use inclined planes to discover the idea of inertia?