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Concept explainers
(a)
Whether the electric field do positive or negative work when the charge
(a)
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Answer to Problem 1CQ
The electric field does positive work when the charge
Explanation of Solution
When we move two opposite charges close together, their initial and final kinetic energies will be zero, so the external force does negative work and the electric field does positive work.
Write the expression for the external work.
Here,
Therefore, the electric field does positive work when the charge
(b)
Whether the potential
(b)
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Answer to Problem 1CQ
The potential increases as
Explanation of Solution
The expression to find the potential is
Therefore, the potential increases as
(c)
Whether the potential energy decreases or increases.
(c)
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Answer to Problem 1CQ
The potential energy decreases.
Explanation of Solution
For charges of opposite signs, the potential energy decreases due to the negative sign in the potential energy term. Thus, the potential energy decreases for two opposite signs approaching each other.
(d)
When the fixed charge is changed to
(d)
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Answer to Problem 1CQ
The electric field does negative work, the potential decrease and the potential energy increases.
Explanation of Solution
When the charges are both negative, the electric field is doing negative work, the repulsion of the charges cause the potential to decrease and the potential energy increases.
Therefore, the electric field does negative work, the potential decrease and the potential energy increases.
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Chapter 17 Solutions
Physics
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- A block of mass m₁ = 10.0 kg is connected to a block of mass m₂ 34.0 kg by a massless string that passes over a light, frictionless pulley. The 34.0-kg block is connected to a spring that has negligible mass and a force constant of k = 200 N/m as shown in the figure below. The spring is unstretched when the system is as shown in the figure, and the incline is frictionless. The 10.0-kg block is pulled a distance h = 22.0 cm down the incline of angle = 40.0° and released from rest. Find the speed of each block when the spring is again unstretched. Vm1 × 1.32 Vm2 = 1.32 × m/s m/sarrow_forwardA block of mass m₁ = 10.0 kg is connected to a block of mass m₂ = 34.0 kg by a massless string that passes over a light, frictionless pulley. The 34.0-kg block is connected to a spring that has negligible mass and a force constant of k = 200 N/m as shown in the figure below. The spring is unstretched when the system is as shown in the figure, and the incline is frictionless. The 10.0-kg block is pulled a distance h = 22.0 cm down the incline of angle 0 = 40.0° and released from rest. Find the speed of each block when the spring is again unstretched. m/s Vm1 Vm2 m/s mi m2 k iarrow_forwardTruck suspensions often have "helper springs" that engage at high loads. One such arrangement is a leaf spring with a helper coil spring mounted on the axle, as in the figure below. The helper spring engages when the main leaf spring is compressed by distance yo, and then helps to support any additional load. Consider a leaf spring constant of 5.45 × 105 N/m, helper spring constant of 3.60 × 105 N/m, and y = 0.500 m. Truck body Dyo Axle (a) What is the compression of the leaf spring for a load of 4.90 × 105 N? m (b) How much work is done compressing the springs? ]arrow_forward
- A skier of mass 75 kg is pulled up a slope by a motor-driven cable. (a) How much work is required to pull him 50 m up a 30° slope (assumed frictionless) at a constant speed of 2.8 m/s? KJ (b) What power (expressed in hp) must a motor have to perform this task? hparrow_forwardA block of mass 1.4 kg is attached to a horizontal spring that has a force constant 900 N/m as shown in the figure below. The spring is compressed 2.0 cm and is then released from rest. a x = 0 x b (a) A constant friction force of 4.4 N retards the block's motion from the moment it is released. Using an energy approach, find the position x of the block at which its speed is a maximum. cm (b) Explore the effect of an increased friction force of 13.0 N. At what position of the block does its maximum speed occur in this situation? cmarrow_forwardA block of mass m = 3.00 kg situated on a rough incline at an angle of 0 = 37.0° is connected to a spring of negligible mass having a spring constant of 100 N/m (see the figure below). The pulley is frictionelss. The block is released from rest when the spring is unstretched. The block moves 11.0 cm down the incline before coming to rest. Find the coefficient of kinetic friction between block and incline. k=100 N/m Ө marrow_forward
- 23. What is the velocity of a beam of electrons that goes undeflected when passing through perpendicular electric and magnetic fields of magnitude 8.8 X 103 V/m and 7.5 X 10-3 T. respectively? What is the radius of the electron orbit if the electric field is turned off?arrow_forward10. A light bulb emits 25.00 W of power as visible light. What are the average electric and magnetic fields from the light at a distance of 2.0 m?arrow_forward9. Some 1800 years ago Roman soldiers effectively used slings as deadly weapons. The length of these slings averaged about 81 cm and the lead shot that they used weighed about 30 grams. If in the wind up to a release, the shot rotated around the Roman slinger with a period of .15 seconds. Find the maximum acceleration of the shot before being released in m/s^2 and report it to two significant figures.arrow_forward
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