Physics Answers

1. Saponification is a process wherein soap is added to a certain type of oil to produce grease. One

such grease is said to have 75.7 % by volume oil and 24.3% by volume soap, wherein the oil and

soap have densities 760 kgm/m3 and 6,250 kgm/m3, respectively. This kind of grease is sold by

packs shaped like a sphere with a diameter of 20 cm for convenience. Calculate: a) the mass of

oil per pack (kgm), b) the mass of soap per pack (kgm),c) the weight of each pack (kgf), d) the

specific weight of grease (N/m3), e) will the grease float if it is placed in water whose density is 1000 kgm/m3? Explain

A magnetic field exerts a force of 8.0 x 10^–14 N toward the west on a proton moving vertically upward at a speed of 5.0 x 10^6 m/s. When moving straight in a northerly direction, the force on the proton is zero. Determine the magnitude and direction of the magnetic field B in this region. (The charge of a proton = 1.6 x 10-19 C, the north direction is into the page.).

An electron moves with an energy of 6.0×10^-16J across a magnetic field of 4.0×10^-3T perpendicularly. Calculate the velocity of electron, force on the electron,orbital radius of the electron and the period of motion.

A jet-fighter flying borizontally in the direction towards south and at an altitude of 5000 feet with speed 400 mi/h drops a bomb which falls down under the force of gravity. Immediately after releasing the weapon the pilot heads his plane to the northeast direction at a supersonic speed of 700 mi/h (a) what is the time the bomb is in the air" (b) How much horizontal distance does the homb covers during the fall? (c) When the bomb hits the ground, what is the distance between the bomb and the jet.

An unclothed person whose body has a surface area of 1.40m^2 with emissivity of 0.85 has a skin temperature of 37°C and stands in a 20°C room. How much energy does the person lose per minute?

Ten kilograms of steam at 100°C is condensed is 500 kg of water at 40.0°C. What is the resulting temperature?

How much heat is required to change 10 g of ice at exactly 0°C to steam at 100°C.

Determine the amount of heat required to boil a 20L of water. How much heat is needed to convert it completely into steam.

(a) A straight conducting wire is placed perpendicularly to the earth

magnetic field at a location. The earth magnetic field at the location has a

magnitude of 0.450 G. Determine the current that must flow in the wire for a

9.50 cm length of the wire to experience a magnetic force of 1.50 N due to the

earth magnetic field.

[1 T = 104 G]

(b) A wire of length 1.0 m carries a current of 1.0 A. The wire is formed into a

circular coil and the circular coil has one turn only. Determine the magnitude of

the maximum torque which is developed on the coil if it is placed in magnetic

field of 2.0 T.