Question

asked 2021-05-20

Assume that a ball of charged particles has a uniformly distributednegative charge density except for a narrow radial tunnel throughits center, from the surface on one side to the surface on the opposite side. Also assume that we can position a proton any where along the tunnel or outside the ball. Let \(\displaystyle{F}_{{R}}\) be the magnitude of the electrostatic force on the proton when it islocated at the ball's surface, at radius R. As a multiple ofR, how far from the surface is there a point where the forcemagnitude is 0.44FR if we move the proton(a) away from the ball and (b) into the tunnel?

asked 2021-05-04

Assume that a 1.00-kg ball is thrown solely by the action of the forearm, which rotates about the elbow joint under the action of the triceps muscle. The ball is accelerated uniformly from rest to 10.0 m/s in 0.350 s, at which point it is released. Calculate (a) the angular acceleration of the arm, and (b) the force required of the triceps muscle. Assume that the forearm has a mass of 3.70 kg and rotates like a uniform rod about an axis at its end.

asked 2021-04-22

Nerve cells are long, thin cylinders along which electric disturbances (nerve impulses) travel. The cell membrane if a typical nerve cell consists of an inner and outer wall separated by a distance of \(\displaystyle{0.10}\mu{m}\). The electric field within the cell membrane is \(\displaystyle{7.0}\cdot{10}^{{{5}}}\) N/C. Approximating the cell membrane as a parallel plate capacitor, determine the magnitude of the charge density on the inner and outer cell walls.

asked 2021-02-19

A 10 kg objectexperiences a horizontal force which causes it to accelerate at 5 \(\displaystyle\frac{{m}}{{s}^{{2}}}\), moving it a distance of 20 m, horizontally.How much work is done by the force?

A ball is connected to a rope and swung around in uniform circular motion.The tension in the rope is measured at 10 N and the radius of thecircle is 1 m. How much work is done in one revolution around the circle?

A 10 kg weight issuspended in the air by a strong cable. How much work is done, perunit time, in suspending the weight?

A 5 kg block is moved up a 30 degree incline by a force of 50 N, parallel to the incline. The coefficient of kinetic friction between the block and the incline is .25. How much work is done by the 50 N force in moving the block a distance of 10 meters? What is the total workdone on the block over the same distance?

What is the kinetic energy of a 2 kg ball that travels a distance of 50 metersin 5 seconds?

A ball is thrown vertically with a velocity of 25 m/s. How high does it go? What is its velocity when it reaches a height of 25 m?

A ball with enough speed can complete a vertical loop. With what speed must the ballenter the loop to complete a 2 m loop? (Keep in mind that the velocity of the ball is not constant throughout the loop).

A ball is connected to a rope and swung around in uniform circular motion.The tension in the rope is measured at 10 N and the radius of thecircle is 1 m. How much work is done in one revolution around the circle?

A 10 kg weight issuspended in the air by a strong cable. How much work is done, perunit time, in suspending the weight?

A 5 kg block is moved up a 30 degree incline by a force of 50 N, parallel to the incline. The coefficient of kinetic friction between the block and the incline is .25. How much work is done by the 50 N force in moving the block a distance of 10 meters? What is the total workdone on the block over the same distance?

What is the kinetic energy of a 2 kg ball that travels a distance of 50 metersin 5 seconds?

A ball is thrown vertically with a velocity of 25 m/s. How high does it go? What is its velocity when it reaches a height of 25 m?

A ball with enough speed can complete a vertical loop. With what speed must the ballenter the loop to complete a 2 m loop? (Keep in mind that the velocity of the ball is not constant throughout the loop).

asked 2021-03-30

A long, straight, copper wire with a circular cross-sectional area of \(\displaystyle{2.1}{m}{m}^{{2}}\) carries a current of 16 A. The resistivity of the material is \(\displaystyle{2.0}\times{10}^{{-{8}}}\) Om.

a) What is the uniform electric field in the material?

b) If the current is changing at the rate of 4000 A/s, at whatrate is the electric field in the material changing?

c) What is the displacement current density in the material in part (b)?

d) If the current is changing as in part (b), what is the magnitude of the magnetic field 6.0cm from the center of the wire? Note that both the conduction current and the displacement currentshould be included in the calculation of B. Is the contribution from the displacement current significant?

a) What is the uniform electric field in the material?

b) If the current is changing at the rate of 4000 A/s, at whatrate is the electric field in the material changing?

c) What is the displacement current density in the material in part (b)?

d) If the current is changing as in part (b), what is the magnitude of the magnetic field 6.0cm from the center of the wire? Note that both the conduction current and the displacement currentshould be included in the calculation of B. Is the contribution from the displacement current significant?

asked 2021-04-03

Consider a point charge with \(\displaystyle{q}={1.5}\times{10}^{{-{8}}}{C}\).

a) What is the radius of an equipotential surface having apotential of 30 V?

b) Are surfaces whose potentials differ by a constant amount (1.0V,say) evenly spaced?

a) What is the radius of an equipotential surface having apotential of 30 V?

b) Are surfaces whose potentials differ by a constant amount (1.0V,say) evenly spaced?

asked 2021-03-26

A pair of forces with equal magnitudes, opposite directions,and different lines of action is called a "couple". When acouple acts on a rigid object, the couple produces a torque thatdoes not depend on the location of the axis. The drawing shows acouple acting on a tire wrench, each force being perpendicular tothe wrench. Determine an expression for the torque produced by thecouple when the axis is perpendicular to the tired and passesthrough (a) point A, (b) point B, and (c) point C. Express youranswers in terms of the magnitude F of the force and the length Lof the wrench

asked 2021-04-27

A charged wire of negligible thickness has length 2L units and has a linear charge density ?. Consider the electric field E? at the point P, a distance d above the midpoint of the wire.

asked 2021-03-24

The figure shows 3 crates being pushed over a concrete floor by a horizontal force f of magnitude 440N. The masses of the cratesare \(\displaystyle{m}_{{1}}={30}\) kg, \(\displaystyle{m}_{{2}}={10}\) kg, and \(\displaystyle{m}_{{3}}={20}\) kg.The coefficient of kineticfriction between the floor and each of the crates is 0.7. a) what is the magnitude \(\displaystyle{F}_{{{32}}}\) of the force on crate 3 from crate 2? b) If the crates then slide onto a polished floor, where the coefficientof kinetic friction is less than 0.700, is magnitude PSKF_{32}ZSL more than,less than, or the same as it was when the coeffient was 0.700?

asked 2021-05-02

Suppose electrons enter the uniform electric field midwaybetween two plates, moving at an upward 45 degree angle as shown.What maximum speed can the electrons have if they are to avoidstriking the upper plate. Ignore fringing of the field. Upper plate is negatively charged bottom plate is positivelycharged length of plate is 6cm and distance from top of top plateto bottom of bottom plate is 1cm.

\(\displaystyle{E}={5.0}\times{10}^{{3}}\frac{{N}}{{C}}\)

\(\displaystyle{E}={5.0}\times{10}^{{3}}\frac{{N}}{{C}}\)