Menu

Physicshelpline

Solution Search

Comments

. June 2016

Combination of lenses

Q- A convex and a concave lens, each of focal length 10 cm are placed at a distance of 10 cm from each other. An object is placed at a distance of 20 cm in front of the convex lens. Find the position of final image and discuss the properties of the final image.

Solutions:

Read more

 Posted in Ray-Optics

Mechanics-NLM

Q- A 6.5 m ladder AB of mass 10 kg leans against a wall as shown. Determine the smallest value of coefficient of static friction between the surfaces (considering same everywhere) for which equilibrium can be maintained.

Solution:

Read more

0 comments
 Posted in NLM

Electromagnetic Waves

Q- A monochromatic light source emits 100w of electromagnetic power uniformly in all directions

a) Calculate the average electric- field energy density 1.00 m from the source.

b) Calculate the average magnetic-field energy density at the same distance from the source.

Solution:

Read more

0 comments
 Posted in EMI

Kepler's Law

Q- A distant star has two planets following circular orbits about the star with one planet four times the distance from the star as the other planet. If the planet closer to the star has a period of 2 years, determine the period of the planet farther from the star.

Solution:

Read more

0 comments
 Posted in Gravitation

de Broglie Wavelength

Q- What is the wavelength of an electron of energy (a) 20 eV (b) 200 eV (c) 2.0 keV

Solution:

Read more

0 comments
 Posted in Modern Physics

Projectile Motion

Q- Suppose the water at the top of Niagara Falls has a horizontal speed of 3.00 m/s just before it cascades over the edge of the falls. At what vertical distance below the edge does the velocity vector of the water point 60.0° below the horizontal?

Solution:

Read more

0 comments
 Posted in Motion_2D

Combination of lenses

Q- Two converging lenses, each with focal length 20 cm are separated by a distance of 60 cm. Calculate the location of the final image of an object placed 90 cm in front of the first lens. Describe the properties of the image. Calculate the overall magnification.

Solution:

Read more

0 comments
 Posted in Ray-Optics

Gravitation

Q- At what altitude above the Earth's surface would your weight be three-fourths of what it is at the Earth's surface? Assume re = 6.371*103 km.

Solution:

Read more

0 comments
 Posted in Gravitation

Relativity

Q- What is the percentage change in momentum of a proton that accelerates from (a) 0.45c to 0.80c and (b) 0.80c to 0.98 c.

Solution:

Read more

0 comments
 Posted in Modern Physics

Transformers

Q- A high intensity desk lamp uses a bulb rated 40W but requires only 12V. It contains a transformer that converts 120V household voltages.

a) Is the transformer step-up or step-down?

b) What is the current in the secondary when the lamp is switched on?

c) What is the current in the primary when …

Read more

0 comments
 Posted in EMI

Thermal Radiations

Q- The radius of the Sun is 6.96 x 108 m and the total power output from its surface is 2.51 x 1026 W.
(a) Assuming that the Sun acts like a black body, calculate its surface temperature.
(b) What is the maximum wavelength of radiation from the Sun?

Solution:

Read more

0 comments
 Posted in Heat and Thermodynamics

Poynting Vector

Q- When a high-power laser is used in the Earth's atmosphere, the electric field of the laser beam can ionize the air, turning it into conducting plasma that reflects the laser light. In dry air at 0°C and 1 atm, electric breakdown occurs for fields with amplitudes above about 3.00 MV/m.

a) What l…

Read more

0 comments
 Posted in EMI

Friction

Q- A 7gram bullet moves horizontally at 1000m/s toward a 5 kg block that is at rest on a horizontal tabletop. The bullet emerges from the block moving to the right at 400m/s. Determine how far the block will slide if the coefficient of kinetic friction between the block and the table is 0.3, assumin…

Read more

0 comments
 Posted in NLM

Current Electricity

Q- In the circuit below

a) Find the current in the 4Ω resistor.

b) What is the power dissipated in this resistor?

Solution:

Read more

0 comments
 Posted in Current Electricity

Heat Engine

Q- One mole of an ideal monatomic gas is used as the working substance in an engine. The engine operates on the cycle shown in the diagram. Processes BC and DA are reversible and adiabatic. What is the efficiency of the engine?

Solution:

Read more

0 comments
 Posted in Heat and Thermodynamics

Motion in 1D

Q- A police car is traveling at a velocity of 18.0 m/s due north, when a car zooms by at a constant velocity of 41.0 m/s due north. After a reaction time 0.900 s the policeman begins to pursue the speeder with an acceleration of 4.00 m/s2. Including the reaction time, how long does it take for the p…

Read more

0 comments
 Posted in Motion_1D

Kirchhoff's Law

Q- Consider the circuit give bellow -

a) Neglecting the internal resistances of the batteries, find the current in the circuit.

b) What power is delivered to each of the resistors?

c) What power is delivered by the 12V battery?

d)What power is delivered by 6V battery?

Solution:

Read more

0 comments
 Posted in Current Electricity

Gravitation

Q- Four identical point particles (each having mass m=5000kg) are located at the points (-2,0), (0,8), (6,0) and (0,3) in the xy plane. All positions are measured in meters. Determine the magnitude of the total gravitational force on the particle located at (6,0) due to the other three particles.

S…

Read more

0 comments
 Posted in Gravitation

Photoelectric Effect

Q- The threshold wavelength for emission of electrons from a given surface is 320nm.

a) What will be the maximum kinetic energy of ejected electrons when the wavelength of the incident light is changed to 350nm.

b) What will be the maximum kinetic energy of ejected electrons when the wavelength of…

Read more

0 comments
 Posted in Modern Physics

Fluids

Q- A sniper fires a rifle bullet into a water tank, making a hole, 53m below the surface of the water. The tank was sealed and is under 3.10 atm of absolute pressure. At what speed does the water begin to shoot out of the hole?

Solution:

Read more

0 comments
 Posted in Fluid
20 .
« Newer |