If electricity costs 9AkWh how much does it cost to burn a 9

If electricity costs 9A/kWh, how much does it cost to burn a 95 W bulb for one day? A 1300 W heater for a sauna requires 40 min to heat the sauna to 190^degree F. What does this cost if electricity sells for 8A/kwh? A Foucault pendulum with a length of25 m has a period of 54 s. What is its frequency? A spring hanging from the ceiling has an unstretched length of 80 cm. A mass is then suspended at rest from the spring causing its length to increase to 89 cm. The mass is pulled down an additional 9 cm and released. What is the amplitude of the resulting oscillation? What is the period of a 0.35 kg mass suspended from a spring with a spring constant of 34 N/m? A boy with a mass of 50 kg is hanging from a spring with a spring constant of 190 N/m. With what frequency does the boy bounce up and down? A pendulum has a length of 30 m. what is its period? A girl with a mass of 40 kg is swinging from a rope with a length of 2.4 m. What is the frequency of her swinging? experiences a force of 14 N directed east. What is the electric field (magnitude and direction) at the location of the charge? Find the force (magnitude and direction) on a -20 mC charge that replaces the 5 mC charge.

Solution

19

Energy=power *time=1300*(40/60)=866.67 Wh=0.86667 KWh

cost=8*0.86667=6.93 A

1.

frequency=1/period=0.0185 Hz

2.amplitude=9 cm

3

w=sqrt(k/m)=9.85

time period=2*pi/w=0.64 sec

5.

w=sqrt(k/m)=1.949

frequency=w/2pi=0.31 Hz

6

period=2*pi*sqrt(l/g)=11 sec