A 8.0-cm-diameter disk emits light uniformly from its surface. 20 cm from this disk, along its axis, is an 9.0-cm-diameter opaque black disk; the faces of the two disks are parallel. 20 cm beyond the black disk is a white viewing screen. The lighted disk illuminates the screen, but there�s a shadow in the center due to the black disk. What is the diameter of the completely dark part of this shadow?

A person pushes a 14.6-kg shopping cart at a constant velocity for a distance of 26.8 m on a flat horizontal surface. She pushes in a direction 26.8 ° below the horizontal. A 39.0-N frictional force opposes the motion of the cart. (a) What is the magnitude of the force that the shopper exerts? Determine the work done by (b) the pushing force, (c) the frictional force, and (d) the gravitational force.

Any tips on how to learn Quantum Mechanics effectively?

A simple pendulum with mass m = 1.8 kg and length L = 2.69 m hangs from the ceiling. It is pulled back to an small angle of θ = 8.7° from the vertical and released at t = 0.

1) What is the period of oscillation?

2) What is the magnitude of the force on the pendulum bob perpendicular to the string at t=0?

3) What is the maximum speed of the pendulum?

4) What is the angular displacement at t = 3.65 s? (give the answer as a negative angle if the angle is to the left of the vertical)

5) What is the magnitude of the tangential acceleration as the pendulum passes through the equilibrium position?

6) What is the magnitude of the radial acceleration as the pendulum passes through the equilibrium position?

7) Which of the following would change the frequency of oscillation of this simple pendulum?

increasing the mass

decreasing the initial angular displacement

increasing the length

hanging the pendulum in an elevator accelerating downward

Two cylindrical iron rods both at temperatureThave lengthsLand 2L, and radiiRandR/2, respectively. If the rods’ temperatures are raised to 3T, and forces are appliedto prevent the rods from changing length, what is the ratio of the forces on the tworods?

A sheet of charge with ρS = 8 nC/m2
is in the plane x = 5 in free space and a line
charge ρL = 15 nC/m is located at x = 2, z = 5.
a. Find E at P(0, 0, 0)
b. E at (4, 5, 6)
c. What is the force per unit length on the line charge?

A soccer player takes a corner kick, lofting a stationary ball 36.0° above the horizon at 16.0 m/s. If the soccer ball has a mass of 0.425 kg and the player's foot is in contact with it for 4.80 ✕ 10⁻² s, find the x- and y-components of the soccer ball's change in momentum and the magnitude of the average force exerted by the player's foot on the ball.

(a)

the x- and y-components of the soccer ball's change in momentum (in kg · m/s)

Δp_x

= kg · m/s

Δp_y

= kg · m/s

(b)

the magnitude of the average force exerted by the player's foot on the ball (in N)

N

You have been hired as a technical consultant for an early-morning cartoon series for children to amke sure that the science is correct. In the script, a wagon containing two boxes of gold (total mass of 150kg) has been cut loose from the horses by an outlaw. The wagon starts from rest 50 meters up a hill with a 6 degree slope. The outlaw plans to have the wagon roll down the hill and across the level fround and then crash into a canyon where his confederates wait. But in a tree 40 meters from the edge of the canyon wait the lone ranger (mass 80kg) and Tonto (mass 70kg). They drop vertically into the wagon as it passes beneath them. The script states that it takes the lone ranger and tonto 5 seconds to grab the gold and jump out of the wagon, but is this correct? You assume that the wagon rolls with negligeble friciton.

A block with a mass of m = 33 kg rests on a frictionless surface and is subject to two forces acting on it. The first force is directed in the negative x-direction with a magnitude of F1 = 11.5 N. The second has a magnitude of F2 = 23 N and acts on the body at an angle θ = 22° measured from horizontal, as shown. write an expression for the component of net force, Fnet,x, in the x direction, in terms of the variables giving in the problem statement. write an expression for the magnitube of the normal force, Fn, acting on the block, F2 and the other variables of the problem. Assume that the surface it rests on it rigid. Find the block's acceleration in the x-direction, ax, in meters per second squared

How is the direction of torque perpendicular to the plane of rotation (according to the cross product of F and r)? It seems very counterintuitive and doesn't seem to make sense.

Consider the following:

If two equal mass objects had the same change in kinetic energy during an interval, then they were acted on by the same net force for that interval.

(a) Is this statement valid? __________

(b) If you contend the statement is valid, how do you know?



(c) If you contend the statement is invalid, what is wrong with it?




(d) If the statement is invalid, restate it to give a valid statement.




(e) Is the valid statement (original, or your revision) a conditional or a bi-conditional? How do you know?

Water molecules have a dipole moment of 6.2 x 10-30 C-m because oxygen is more electronegative than hydrogen. If a water molecule sits at the origin and an electron sits at x= 10 nm, what is the magnitude of the force on the electron in fN? "f" is for femto b. In which direction is the force on the electron at x = 10 nm? c. What is the force on an electron that sits at y = 10 nm in fN? d. In which direction is the force on the electron at y = 10 nm?