UA-78309841-1
Menu

Physicshelpline

. April 2017

Wave Motion

Q- In the oceans, whales communicate by sound transmission through the water. A whale emits a sound of 60 Hz to tell a wayward calf to catch up to the pod. The speed of sound in water is about 1500 m/s.

(a) How long does it take the sound to reach the calf if he is 1.46 km away?

(b) What is the wa…

Read more

Matter Waves: de Broglie Wavelength

Q- Electrons with a speed of 2.5 *106 m/s pass through a double-slit apparatus. Interference fringes are detected with a fringe spacing of 1.6 mm.

(a) What will the fringe spacing be if the electrons are replaced by neutrons with the same speed?

(b) What speed must neutrons have to produce interfe…

Read more

NLM: Friction

Q- A block of mass 40 kg is place on an incline surface making angle 300 with horizontal. If the coefficient of friction between the block and the surface is 0.2, find the minimum horizontal force P required to push the block up the incline.

Solution:

Read more

Ray Optics: Refraction

Q- A fish in a flat-sided aquarium sees a can of fish food on the counter. To the fish's eye, the can looks to be 30 cm outside the aquarium. What is the actual distance between the can and the aquarium? (You can ignore the thin glass wall of the aquarium.)

Solution:

Read more

Impulse and Momentum

Q- (a) What is the impulse needed to stop a 20 kg bowling ball moving at 5 m/s?

(b) A 2000 kg car accidentally drops from a crane and crashes at 30 m/s to the ground below and comes to an abrupt halt. What is the momentum at impact?

(c) A railroad diesel engine weighs two times as much as a freig…

Read more

Momentum and Energy

Q- Two blocks of masses M and 3M are placed on a horizontal, frictionless surface. A light spring is attached to one of them, and the blocks are pushed together with the spring between them. When the blocks released, the block of mass 3M moves to the right with a speed of 2.00m/s

(a) What is the …

Read more

Wave Optics - Polarization

Q- Un-polarized light enters a series of three polarizers. The axis of polarization of second makes an angle of 60 degree with that of first and the angle between the axes of second and third is 45 degree. What percentage of the initial intensity of light is transmitted through the system of polariz…

Read more

Rotational Motion

Q- A light cable is used to pull a block of mass 10 kg on a rough horizontal surface (coefficient of friction 0.2). The cable is passed through a fixed pulley of radius 0.25 m and moment of inertia 1.2 kg-m2, which is free to rotate about its horizontal axis. The cable is horizontal between the pull…

Read more

Electromagnetic Waves

Q- An electromagnetic wave has a frequency of 110 MHz and is traveling in a vacuum. The magnetic field is given by                                    (z, t) = (2.00 x 10-8 T) cos (k z - ω t) i.

(a) Find the wavelength and the direction of propagation of this wave.

(b) Find t…

Read more

Sound Waves

Q- Figure shows a snapshot graph at t = 0 s of a 30.0 Hz wave traveling to the left. Each interval on the vertical axis corresponds to 5 mm. 

(a) What is the wave speed?

(b) What is the phase constant of the wave?

(c) Write the displacement equation for this wave.

Solution:

Read more

Coulomb's Law

Q- Six point charges, four positive (+q) and two negative (-q), are fixed at the positions shown in the x-y plane; q = 2 × 10-6 C and a = 0.88 m. A test charge Q = 1.5 × 10-6 C is at the origin. Find the x- and y-components of the total force on Q.

Solution:

Read more

Wave Optics: Michelson Interferometer

Q- Light of wavelength 602.446 nm is used in a Michelson interferometer. When the mirror M2 is slowly moved, shifting of 33198 bright fringes is observed. By what distance mirror M2 is moved?  

Solution:

Read more

Elasticity

Q- Two cylindrical rods, one of steel and the other of brass, are joined at C and restrained (fixed) by rigid supports at A and E with their natural lengths as shown in the figure. Now forces of 60 kN and 40 kN are applied at points B abd D resoectively. Knowing that E(steel)=200 GPa and E(brass)=10…

Read more

Electromagnetic induction

Q- A long straight wire carrying a current of I1 = 30 A is paced in the plane of a rectangular wire loop and parallel to its nearest side of length l = 30 cm, at a distance of a = 1 cm. The width of the loop is b = 8 cm. Find the magnitude of the net force on the loop if the current in the loop is I

Read more

Rotational Motion

Q- A wad of sticky clay with mass m and velocity vi is fired at a solid cylinder of mass M and radius R. The cylinder is initially at rest and is mounted on a fixed horizontal axle that runs through its center of mass. The line of motion of the projectile is perpendicular to the axle and at a distan…

Read more

Electrostatics: Field and Force

Q- Throughout space there is a uniform electric field in the - y direction of strength E = 550 N/C. There is no gravity. At t = 0, a particle with mass m = 2 g charge q = -11 µC is at the origin moving with a velocity v0 = 45 m/sat an angle q = 25° above the x-axis.

(a) What is the magnitude of …

Read more

16 .