Mechanics | Relativity Answers

An electric filament lamp with a clear glass bulb when switched on gives a bright white light. The bulb contains a small quantity of argon gas. Briefly describe the parts played by conduction convection and radiation in the loss of heat from the lamp filament.

A 100 gram mass of brass was heated to 100⁰C and then places in a styrofoam cup containing 150 grams of paraffin at 20^oC. After stirring the final temperature reached 29^oC.

i. Determine the specific heat of paraffin

ii. State one assumption you made in your calculations in (i.) above.

[specific heat capacity of brass = 3806jkg^-1K^-1]

i. Distinguish between gauge pressure and absolute pressure.

ii A U-tube mercury manometer is used to measure the pressure of a gas in a metal container. If the gauge pressure of the gas is 13 kPa what will be the difference mercury levels in the two arms of the U-tube.

Density of mercury = 13600 kg/m3

Atmospheric pressure = 101 kPa

Air is compressed in a cylinder of a diesel engine. The initial volume of the air is 800cm³ and a temperature of 27^oC and a pressure of 100kPa. The air compressed to one-fifteenth of its initial volume so that its temperature reaches 600^oC. Determine the final pressure of the air.

In a test on machine an effort of 50N was required to raise a load pf 250N. If the effort moves through 150 mm to raise the load by 25 mm, find the following:

i. The Mechanical Advantage

ii. The Velocity Ratio

iii. The efficiency

iv. The work done by the effort.

v. The work done in raising the load 25 mm.

vi. The power developed by the effort over a period of 5 seconds

Sketch a stress-strain graph for mild steel and identify the following points:

i. The proportional limit stress

ii. The yield stress

iii. The stress at the elastic limit

iv. The ultimate tensile stress

v. Also identify the elastic region and the plastic region on your graph

A 50 kg wooden box is pulled up a plane inclined at 30^o to the horizontal with an acceleration of 5ms^-2. The pulling force, P, is applied parallel to the plane and the coefficient of kinetic friction between the box and the plane is 0.3.

i. Draw a diagram showing all the forces acting on the wooden box.

ii. Find the normal reaction, N_A

iii. Find the pulling force, P.

iv. If the wooden box was pulled with a constant velocity, determine the pulling force that would be required to pull the box up the incline

State the meaning of the following terms:

i. Coefficient of Kinetic Friction

ii. Limiting Friction Force

A pile driver of mass 350 kg falls freely from a height of 2.8 m and strikes an 80 kg pile. Determine the:

i. common velocity of the pile and driver after the impact

ii percentage loss of kinetic energy after the impact

The flywheel of an electric motor accelerates from rest to a speed of 1000 rev/min in 10 seconds. The motor was then allowed to run for 1 minutes. The power was then switched off and the flywheel turns a further 400 rev before coming to rest.

i. Sketch the ω-t graph for the motion of the flywheel.

ii. Calculate the initial acceleration

iii. Find the time taken for the flywheel to come to rest after the power was switched off.