Question 4356:

• NECO 2000

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 4357:

• NECO 2000

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 4358:

• NECO 2000

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 4359:

• NECO 2000

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 4360:

• NECO 2000

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