# A person accidentally leaves a car with the lights on. If eachof the two headlights uses 43 W andeach of the two taillights 7.0 W,for a total of 1.0E2 W, how longwill a fresh 12-V battery last if it is rated at 8.0E1 A·h? Assume the full 12 V appears across each bulb.

Question
Other
A person accidentally leaves a car with the lights on. If eachof the two headlights uses 43 W andeach of the two taillights 7.0 W,for a total of 1.0E2 W, how longwill a fresh 12-V battery last if it is rated at 8.0E1 A·h?
Assume the full 12 V appears across each bulb.

2021-05-07
P = 100W
1 A*h = 3600 A*s (Coulombs), therefore:
Q = 288000 C
E = 12 V
For a battery, P=EI.
$$\displaystyle{I}=\triangle\frac{{Q}}{\triangle}{t}$$
Transposing these equations and solving for $$\displaystyle\triangle{t}$$ the followingequation resolves:
$$\displaystyle\triangle{t}=\frac{{{E}\triangle{Q}}}{{P}}={34560}{s}={9.6}$$ hours (So that's why theyhad it in A*h originally)

### Relevant Questions

A wagon with two boxes of Gold, having total mass 300 kg, is cutloose from the hoses by an outlaw when the wagon is at rest 50m upa 6.0 degree slope. The outlaw plans to have the wagon roll downthe slope and across the level ground, and then fall into thecanyon where his confederates wait. But in a tree 40m from thecanyon edge wait the Lone Ranger (mass 75.0kg) and Tonto (mass60.0kg). They drop vertically into the wagon as it passes beneaththem. a) if they require 5.0 s to grab the gold and jump out, willthey make it before the wagon goes over the edge? b) When the twoheroes drop into the wagon, is the kinetic energy of the system ofthe heroes plus the wagon conserved? If not, does it increase ordecrease and by how much?
A dead battery is charged by connecting it to the live battery ofanother car with jumper cables. Assume that V=9.5 V and R=0.90 Ohms.
Determine the current in the starter.
Determine the current in the dead battery.
The dominant form of drag experienced by vehicles (bikes, cars,planes, etc.) at operating speeds is called form drag. Itincreases quadratically with velocity (essentially because theamount of air you run into increase with v and so does the amount of force you must exert on each small volume of air). Thus
$$\displaystyle{F}_{{{d}{r}{u}{g}}}={C}_{{d}}{A}{v}^{{2}}$$
where A is the cross-sectional area of the vehicle and $$\displaystyle{C}_{{d}}$$ is called the coefficient of drag.
Part A:
Consider a vehicle moving with constant velocity $$\displaystyle\vec{{{v}}}$$. Find the power dissipated by form drag.
Express your answer in terms of $$\displaystyle{C}_{{d}},{A},$$ and speed v.
Part B:
A certain car has an engine that provides a maximum power $$\displaystyle{P}_{{0}}$$. Suppose that the maximum speed of thee car, $$\displaystyle{v}_{{0}}$$, is limited by a drag force proportional to the square of the speed (as in the previous part). The car engine is now modified, so that the new power $$\displaystyle{P}_{{1}}$$ is 10 percent greater than the original power ($$\displaystyle{P}_{{1}}={110}\%{P}_{{0}}$$).
Assume the following:
The top speed is limited by air drag.
The magnitude of the force of air drag at these speeds is proportional to the square of the speed.
By what percentage, $$\displaystyle{\frac{{{v}_{{1}}-{v}_{{0}}}}{{{v}_{{0}}}}}$$, is the top speed of the car increased?
Express the percent increase in top speed numerically to two significant figures.
A typical small flashlight contains two batteries, each having emf of 1.50 V connected in series with a bulb having a resistance of 14.0.
Part A
If the internal resistance of the battery is negligible, what power is delivered to the bulb?
Part B
If the batteries last for a time of 5.70 h, what is the total energy delivered to the bulb?
Part C
The resistance of real batteries increases as they run down.If the initial internal resistance is negligible,what is the combined internal resistance of both batteries when the power to the bulb has decreased to half its initial value? (Assume that the resistance of the bulb is constant. Actually, it will change some what when the current through the filament changes,because this changes the temperature of the filament and hence there sistivity of the filament wire.)
How do you solve this problem? I don' t even know whereto begin.
A Ferrari with a mass of 1400 kg approaches a freeway underpassthat is 10 m across. At what speed must the car be moving, inorder for it to have a wavelength such that it might somehow"diffract" after passing through this "single slit"? How dothese conditions compare to normal freeway speeds of 30m/s?

A wind farm generator uses a two-bladed propellermounted on a pylon at a height of 20 m. The length of eachpropeller blade is 12 m. A tip of the propeller breaks offwhen the propeller is vertical. The fragment flies offhorizontally, falls, and strikes the ground at P. Just beforethe fragment broke off, the propeller was turning uniformly, taking1.2 s for each rotation. In the above figure, the distancefrom the base of the pylon to the point where the fragment strikesthe ground is closest to:
a) 130 m
b) 160 m
c) 120 m
d) 140 m
e) 150 m
At an airport, luggage is unloaded from a plane into threecars of a luggage carrier. The acceleration of the carrier is $$\displaystyle{0.12}\frac{{m}}{{s}^{{{2}}}}$$, and friction is negligible. The coupling bars havenegligible mass. By how much would the tension in each of thecoupling bars A,B, and C change if 39kg of luggage were removedfrom car 2 and placed in (a) car 1 and (b) car 3? If the tensionchanges, specify whether it increases or decreases.
A helicopter carrying dr. evil takes off with a constant upward acceleration of $$\displaystyle{5.0}\ \frac{{m}}{{s}^{{2}}}$$. Secret agent austin powers jumps on just as the helicopter lifts off the ground. Afterthe two men struggle for 10.0 s, powers shuts off the engineand steps out of the helicopter. Assume that the helicopter is infree fall after its engine is shut off and ignore effects of airresistance.
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?