Physics Answers

3. Calculate

a. The force on an electron which is stationary in

I. A magnetic field of flux density 2.5T

ii. An electric field of intensity 1000V/m

b. The force on an electron moving with a velocity of 1.5×10^6m/s at right angles to

I. A magnetic field of flux density 1.5T

ii. An electric field of intensity 2000V/m

An electron moving 5.0×10^6m/s is shot parallel to an electric field of strengHth 1×10^3N/c Arranged so as to retard its motion

a. How far will the electron travel in the field before coming momentarily to rest.

b. If the field ends suddenly after 0.75cm, what fraction of its initial energy will the electron lose in passing through it.

2. A vaccum diode contsists of a cylindrical cathode of radius 0.05cm mounted coaxially inside a cylindrical anode of radius 0.45cm. If the anode-cathode voltage is 400V and the electron leaves the anode with zero speed, calculate its speed when it strikes the anode. What is the flux density of the magnetic field that must be applied along the axis in order to just prevent the electrons from striking the anode?

Estimate the rise in temperature of the brack discs in a car of mass 1200kg traveling at 30m/s which is brought to rest by the application of the breakers alone. The brake discs have a total mass of 5kg. Assume that there is no heat loss and that the marterial of the four brake discs has a specific heat capacity of 800J/kg/k

A 50kg boy wanted to get a coconut from the tree. He can do this in two ways: (a) he can climb the tree or (b) use a ladder of length L= 39.37 ft and inclined 30° with the horizontal. The height of the tree is 6m. Find the work done by the gravitational force on the boy in each case.

EWhen a block of metal of mass 0.11kg and specific heat capacity 400J/kg/k is Heated to 100°c and quickly transferred to a calorimeter containing 0.20kg of a liquid at 10°c the resulting temperature of 18°c. On repeating the experiment with 0.40kg of liquid in the same container and at the same initial temperature of 10°c the resulting temperature is 14.5°c. Calculate a. The specific heat capacity of the liquid b. The thermal capacity of the container.

Three charges, +5Q, -5Q, and +3Q are located on the y-axis at y = +4a, y = 0, and y=-4a , respectively. The point P is on the x-axis at x = 3a. (a) How much energy did it take to assemble these charges? (b) What are the x, y, and 2 components of the electric field Ę at P? (c) What is the electric potential V at point P, taking V = 0 at infinity? (d) A fourth charge of +Q is brought to P from infinity. What are the x, y, and z components of the force F that is exerted on it by the other three charges? (e) How much work was done (by the external agent) in moving the fourth charge +Q from infinity to P?

2. Two forces F1 and F2 act on a particle. The force F1 has magnitude 8 N and acts due east. The resultant of F1 and F2 is a force of magnitude 14 N acting in a direction whose bearing is 120q. Find (i) the magnitude of F2 , (4) (ii) the direction of F2 , giving your answer as a bearing to the nearest degree.

explain what is meant by the statement that electrostatic forces obey the principle of superposition

A stone is thrown downward at 30 m/s. What is its speed, [2]

a)after 1s b) after 2s

What is the airspeed of a laden swallow?