Physics Past Questions and Answers

400g of cold water is added to 200g of water at 70°C. If they are properly mixed and the temperature of the mixture is 300°C. calculate the initial temperature of the cold water. (Neglect the heat absorbed by the container)

A 10°C
B 15°C
C 20°C
D 30°C
E 40°C

Question 37:

The heat from a fire in a closed room reaches someone far away in the room, mainly by ____________

A Reflection
B Diffusion
C Conduction
D Radiation
E Convection

Question 38:

A solid weights 5.0 N in air, 4.2 N in water and 4.4 N in liquid Y. Calculate the relative density of liquid Y.

A 0.75
B 0.88
C 0.95
D 1.13
E 1.33

Question 39:

Two forces forming a couple are separated by a distance of 25cm. If one of the forces equals 40N, what is the moment of the couple?

A 1000 Nm
B 500 Nm
C 10 Nm
D 5 Nm
E 1.6 Nm

Question 40:

A radioactive substance has a half-life of 3 minutes. After 9 minutes, the count rate was observed to be 200. What was the count rate at zero time?

A 200
B 1200
C 1600
D 2400
E 4800