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  • please help physics!!!!!!!!!!!!!!!!!!!?

    A large fish tank is filled with water (of refractive index 1.33). One side of the tank is made of a parallel-sided piece of glass. A ray of light strikes the glass from the outside at an angle of incidence of 44degrees.

    Estimate the angle through which this ray is deviated as it emerges into the water. Just give the magnitude of the deviation, there's no need for signs.

    1 AnswerPhysics8 years ago
  • A circular loop of wire of area 1.3m^2 is held fixed with its plane horizontal. At a certain instant ( t= 0) a?

    A circular loop of wire of area 1.3m^2 is held fixed with its plane horizontal. At a certain instant ( t= 0) a uniform vertical magnetic field B is switched on. The magnetic field increases linearly with time, t

    Suppose that, for t= 3.96 ,B = 2.2T . What is the induced voltage ?

    1 AnswerPhysics8 years ago
  • Two long parallel wires, each carrying a current of 20mA , are held 140mm apart in vacuum.?

    Two long parallel wires, each carrying a current of 20mA , are held 140mm apart in vacuum. The currents in the wires flow in opposite directions.

    a) What is the force per unit length on each wire due to the other ?Take the magnetic permeability of free space to be 4pi*10^-7

    give answer in newtons per metre

    1 AnswerPhysics8 years ago
  • A student carelessly makes contact simultaneously with both terminals of a 2.3kV power supply (one hand touche?

    A student carelessly makes contact simultaneously with both terminals of a 2.3kV power supply (one hand touches the positive terminal, the other the negative). The resistance provided by the student's body is 90kohms .

    a) What power is generated in the student's body?

    Give your answer in Watts.

    b) What resistance needs be connected in series with the power supply so that the current drawn by the student would have been limited to the (much safer) value of 2.0mA ?

    Give your answer in kohms

    2 AnswersPhysics8 years ago
  • A 90 resistor and a length of wire of resistance 25 are connected in series across a 40 power supply.?

    A 90ohms resistor and a length of wire of resistance 25ohms are connected in series across a 40V power supply.

    A) Calculate the power dissipated (i) in the 90 resistor and (ii) in the 25 wire. IN WATTS

    B) Calculate the power produced by the power supply IN WATTS

    3 AnswersPhysics8 years ago
  • . please help .. A small water drop with a charge of 100 times that of the electron?

    A small water drop with a charge of 100 times that of the electron is prevented from falling (in a vacuum) by an electric field E= 1.5×10^5Vm^-1

    .What is the mass of the drop ?

    Give your answer in kg. Remember that the acceleration due to gravity, g= 9.8ms^-2 , and the charge on a single electron is −1.6×10−19C .

    1 AnswerPhysics8 years ago
  • uniform electric field with a magnitude of 6300Vm^-1 points in the positive x direction?

    uniform electric field with a magnitude of 6300Vm^-1 points in the positive x direction.

    1) Find the change in electric potential energy when a +20.0C charge is moved 6.50Ccm in the positive direction. Give your answer in Joules. Remember, 1C = 1*10-6 C.

    2) Find the change in electric potential energy when a +20.0C charge is moved 6.50cm in the negative x direction. Give your answer in Joules.

    2 AnswersPhysics8 years ago
  • certain molecule can be considered to be an electric dipole comprising 2 point charges, one of charge +1.6 x 1?

    certain molecule can be considered to be an electric dipole comprising 2 point charges, one of charge +1.6 x 10-19 C and the other of charge -1.6 x 10-19 C separated by a distance of 4.1×10−12m .the molecule is placed in a uniform electric field of strength 1.4×105Vm^-1, what is the magnitude of the force experienced by each of the charges, due to the electric field?

    Give your answer in Newtons

    1 AnswerPhysics8 years ago
  • In the Bohr model of the hydrogen atom, an electron of mass 9.1×10^−31kg and charge -1.6×10^−19C is considered?

    .In the Bohr model of the hydrogen atom, an electron of mass 9.1×10^−31kg and charge -1.6×10^−19C is considered to be moving at a constant speed of 2.2×10^6ms^-1 in a circular orbit of radius 5.3×10−11m around a proton of mass 1.67×10−27kg and charge +1.6×10−19C

    A) Calculate the centripital force, (mv2)/r, necessary to keep the electron moving in its orbit.Give your answer in Newtons.

    B)Calculate the electrostatic force acting on the electron due to the proton.Give your answer in Newtons.

    C)Are the forces equal (within 2%)? (Remember to check both magnitude and direction.)

    Select one of the options below.

    YES OR NO

    1 AnswerPhysics8 years ago
  • A room measures 3m*5m* 5m.Approximately how many molecules of air are in the room ?

    A room measures 3m*5m* 5m .Approximately how many molecules of air are in the room ? Take room temperature to be 25degrees and the pressure to be 1.0×105Pa , and Boltzmann's constant to be 1.38×10−23JK^-1 . Remember to convert the temperature to Kelvin.

    Question 2

    Air at atmospheric pressure (1.0×105 ) is compressed at constant temperature in a bicycle pump so that its volume is reduced by a factor of 8.

    a) What is the pressure of the air when compressed ?

    b) What is the area of the piston in the pump, if the force acting on it is 103N ?give your answer in square metres.

    c) If the pressure is sufficient to open the valve but not to pump air into the tyre, what is the pressure in the tyre ?Give your answer in Pascals.

    1 AnswerPhysics8 years ago
  • Mobile phones radiate electromagnetic energy. European regulations recommend these phones deliver no more than?

    Mobile phones radiate electromagnetic energy. European regulations recommend these phones deliver no more than 2 W per kg of body mass (averaged over 10 g of tissue). Assume that a mobile phone radiates energy such that each kg of tissue near the ear receives 0.80W of power. Assume that this energy is used to heat the tissue.

    1) In 1hour of mobile phone use, how much energy does it deposit per kg of tissue ?

    Give your answer in Joules.

    2)If the specific heat capacity of the tissue is the same as that of water (4186JKg^-1degrees^-1 ), what increase in temperature would you expect for the tissue in your head ? Use the answer from part A. Note that, as this ignores heat loss etc., this estimate is an upper limit only.

    Give your answer in C.

    2 AnswersPhysics8 years ago
  • Air at atmospheric pressure (1.0×105Pa ) is compressed at constant temperature in a bicycle pump so that its v?

    Air at atmospheric pressure (1.0×105Pa ) is compressed at constant temperature in a bicycle pump so that its volume is reduced by a factor of 8.

    1) What is the pressure of the air when compressed ?Give your answer in Pascals.

    2)What is the area of the piston in the pump, if the force acting on it is 103N ?Give your answer in square metres.

    3)If the pressure is sufficient to open the valve but not to pump air into the tyre, what is the pressure in the tyre ?Give your answer in Pascals.

    QUESTION 2

    An air bubble has a volume of 1.5cm^3 when it is at the bottom of a lake 35m deep. The bubble rises to the surface where the temperature is 20^{\circ}C, the pressure is 1.0×105Pa (equal to atmospheric pressure, since just below the surface) and the volume of the bubble just below the surface is 7.0cm^3 .

    1)Assuming that the density of water is independent of temperature and pressure, what is the pressure at the bottom of the lake ? Include the effects of atmospheric pressure.

    Give your answer in Pascals. Take the density of water to be 1000kg\ m^{-3} , and the acceleration due to gravity to be 9.8m\ s^{-2} .

    2)Assuming that the temperature of the air in the bubble is the same as that of the surrounding water, estimate the temperature at the bottom of the lake. Remember to convert to and from Kelvin in this part.Give your answer in oC.

    QUESTION 3

    A room measures 3m * 5m * 5m .Approximately how many molecules of air are in the room ? Take room temperature to be 25^{\circ}C and the pressure to be 1.0×105Pa , and Boltzmann's constant to be 1.38×10−23J\ K^{-1} . Remember to convert the temperature to Kelvin.

    QUESTION 4

    While jogging, a 70.0 kg student generates thermal energy at a rate of 1380W . To maintain a constant body temperature of 37.0^{\circ}C, this energy must be removed by perspiration or other mechanisms. If these mechanisms failed and the heat could not flow out of the student's body, irreversible body damage could occur.

    Protein structures in the body are irreversibly damaged if body temperature rises to 44.0^{\circ}C or above. The specific heat of a typical human body is 3480 J kg-1 K-1, slightly less than that of water. (The difference is due to the presence of protein, fat, and minerals, which have lower specific heat capacities.)

    1)If the cooling mechanisms in the body fail, for how long a time t could a student jog before irreversible body damage occurs ?

    Express your answer in minutes.

    1 AnswerPhysics8 years ago
  • Milk in your Tea.If 0.2 l (litre, = 1000 cm3 = 0.001 m3) of tea at 85degrees is added to 0.03 l of milk at 5de?

    Milk in your Tea ?

    If 0.2 l (litre, = 1000 cm3 = 0.001 m3) of tea at 85degrees is added to 0.03 l of milk at 5degrees, what is the final temperature of the mixture ? For simplicity, assume that the specific heat capacity, and density, of tea and milk are ~ the same.

    Give your answer in degrees.

    3 AnswersPhysics8 years ago
  • the depth of the lake is 92m.gas bubble rises from the bottom of the lake in part A to the surface. If its vol?

    gas bubble rises from the bottom of the lake in part A to the surface. If its volume just below the surface is 7.0×10^5m^3 , what the bubble's volume at the bottom of the lake ? Use Boyle's Law - i.e. that the pressure of the gas in the bubble (which equals that of the surrounding water) is inversely proportional to its volume.

    Give your answer in m3.

    Q2. THE MASS of air was found to be 5.25*10^18. Taking the average pressure on the ocean floor to be 4.0×107Pa , calculate the mass of water on the Earth, using the same method you used in part A. Remember that only 70% of the Earth is covered by ocean. Ignore atmospheric pressure. give your answer in kg

    2 AnswersPhysics9 years ago
  • The average atmospheric pressure at ground level is 1.0×105Pa and the Earth is a sphere of radius 6400km .?

    The average atmospheric pressure at ground level is 1.0×105Pa and the Earth is a sphere of radius 6400km . Assume that the acceleration due to gravity, (= 9.8ms^-2 ) is also constant throughout the atmosphere. Estimate the total mass of air in the atmosphere.

    Give your answer in kg.

    Q2. Atmospheric pressure may be assumed to be 1.0×105Pa and the temperature constant throughout a lake. Take the density of water to be 1000kgm^-3 .In what depth of lake would the pressure at the bottom be 10 times that of normal atmospheric pressure ? Remember that, at the surface of the lake, the pressure is already one atmosphere.

    Give your answer in metres. Take the acceleration due to gravity to be 9.8ms^-2 .

    3 AnswersPhysics9 years ago
  • Section of steel railway track has a length of 76 at a temperature of 0 °C. The linear expansivity (alpha) of?

    Section of steel railway track has a length of 76 at a temperature of 0 °C. The linear expansivity (alpha) of?

    section of steel railway track has a length of 76m at a temperature of 0 °C. The linear expansivity (alpha) of steel is 1.2×10−5K^-1 .

    A)By how much would the length increase if the temperature were to rise to 20DEGREES ?Give your answer in metres.

    B)If sections of this track were laid end-to-end from Cork to Dublin (say a distance of 240km ) during the Winter when the temperature was 3.0degrees, by how much would this entire track have expanded during the Summer when the temperature was 20degrees ?Give your answer in km.

    Second Question please

    a) Calculate the area of the Earth covered by ocean. Assume a planetary radius of 6400 km, and remember that only 70 % of the Earth's surface is covered by ocean. Give your answer in square kilometres, km^2.

    b) The Antarctic ice cap has an area of 1.4×107km^2 and an average thickness of 2km . If global warming were to result in this ice melting completely, by how much would the level of the oceans rise ? Assume that all the ice is converted to water. Hint: if this volume of water covered the area calculated in Part A, what height would be required ?

    Note that London, New York, Miami, Bombay, Calcutta, Sydney, Shanghai, Lagos and Tokyo would be largely submerged by a sea level rise of 10 m.Give your answer in metres.

    2 AnswersPhysics9 years ago
  • section of steel railway track has a length of 76 at a temperature of 0 °C. The linear expansivity (alpha) of?

    section of steel railway track has a length of 76 at a temperature of 0 °C. The linear expansivity (alpha) of steel is 1.2×10−5K^-1 .

    A)By how much would the length increase if the temperature were to rise to 20DEGREES ?Give your answer in metres.

    B)If sections of this track were laid end-to-end from Cork to Dublin (say a distance of 240km ) during the Winter when the temperature was 3.0degrees, by how much would this entire track have expanded during the Summer when the temperature was 20degrees ?Give your answer in km.

    Second Question please

    a) Calculate the area of the Earth covered by ocean. Assume a planetary radius of 6400 km, and remember that only 70 % of the Earth's surface is covered by ocean. Give your answer in square kilometres, km^2.

    b) The Antarctic ice cap has an area of 1.4×107km^2 and an average thickness of 2km . If global warming were to result in this ice melting completely, by how much would the level of the oceans rise ? Assume that all the ice is converted to water. Hint: if this volume of water covered the area calculated in Part A, what height would be required ?

    Note that London, New York, Miami, Bombay, Calcutta, Sydney, Shanghai, Lagos and Tokyo would be largely submerged by a sea level rise of 10 m.Give your answer in metres.

    2 AnswersPhysics9 years ago
  • Assume it takes 4.5×10^5J of energy for a kettle to boil a litre of water.The kettle delivers energy at a rate?

    Assume it takes 4.5×10^5J of energy for a kettle to boil a litre of water. The kettle delivers energy at a rate of 4.9kW .

    a)How long does it take for the water to boil ?Give your answer in seconds. Remember, you're given the power in kW, so don't forget to convert this.

    b)The ESB charges 12.6c for each kW hr of electrical energy. How much does it cost to boil this litre of water ?

    Give your answer in cent. Remember, a kW hr is a unit of energy, and is the number of Joules provided by a source running at 1 kW for 1 hour ( 1000W *3600 s =3.6 *10^6 J).

    3 AnswersPhysics9 years ago
  • Europe uses 2.0×10^20J of energy per year.?

    Europe uses 2.0×10^20J of energy per year.

    a) Calculate the rate at which this is used (i.e. the power).Give your answer in W. Remember, there are 365 days in a year.

    b) At the Earths surface, sunlight delivers 1300Wm^-2 of power. Imagine this is collected using very large solar panels, and converted into useful energy with 100 % efficiency. What area of panels is required to provide the power calculated in Part A ?

    Give your answer in m2.

    c)If, instead, the efficiency of the panels is 15 % (typical of the more efficient panels on sale today), what area would be required ?Give your answer in m2.

    1 AnswerPhysics9 years ago
  • Assume it takes 4.5×105J of energy for a kettle to boil a litre of water.The kettle delivers energy at a rate?

    Assume it takes 4.5×105J of energy for a kettle to boil a litre of water. The kettle delivers energy at a rate of 4.9kW .

    a)How long does it take for the water to boil ?Give your answer in seconds. Remember, you're given the power in kW, so don't forget to convert this.

    b)The ESB charges 12.6c for each kW hr of electrical energy. How much does it cost to boil this litre of water ?

    Give your answer in cent. Remember, a kW hr is a unit of energy, and is the number of Joules provided by a source running at 1 kW for 1 hour ( 1000W *3600 s =3.6 *10^6 J).

    3 AnswersPhysics9 years ago