Question
Fig. 5.1 shows a metal block on a flat surface.
(a) (i) The mass of the metal block is 1.6 kg.
Calculate the weight of the metal block.
weight = …………………………………………….. N
(ii) Calculate the pressure on the flat surface due to the metal block.
pressure = ……………………………………… N / \(cm^2\)
(b) In an experiment, the metal block is heated and the temperature of the metal block increases
by 100 °C.
State the effect, if any, of the temperature increase on:
1. the volume of the metal block .
2. the mass of the metal block
3. the density of the metal block
Answer/Explanation
Answer:
(a) (i) (weight =) mass × g OR 1.6 × 10 OR mass = W ÷ g
(weight =) 16 (N)
(ii) (pressure =) force ÷ area
(pressure =) 16 ÷ 18
(pressure =) 0.89 (N / \(cm^2\))
(b) 1 (volume of block) increases
2 (mass) remains constant owtte
3 (density) decreases
Question
Fig. 5.1 shows a glass bottle containing air. The bottle is sealed with a cap.
(a) The air in the bottle becomes warmer.
(i) State what happens to the pressure of the air in the bottle.
(ii) Explain why the pressure of the air in the bottle changes. Use your ideas about gas molecules.
(b) The bottle has a weight of 5.4 N and an area of 9.2 cm2 in contact with the table.
Calculate the pressure produced by the bottle on the table. Give the unit.
pressure =…………………………………………………………
(c) Fig. 5.2 shows another bottle. The bottle is on a table. Part of the base of this bottle is not in contact with the table.
Fig. 5.3 shows the base of the bottle. The shaded area is not in contact with the table.
(i) The base of the bottle is circular. The radius of the outer circle is 4.0 cm as shown in Fig. 5.3. Calculate the area of this circle.
(ii) The bottle shown in Fig. 5.2 has the same mass as the bottle shown in Fig. 5.1. Explain why the bottle shown in Fig. 5.2 exerts more pressure on the table than the bottle shown in Fig. 5.1.
Answer/Explanation
Answer:
(a)(i) (pressure) increases
(a)(ii) any four from:
(air) molecules / particles have more (kinetic) energy / move faster
more frequent collisions
harder collisions (with walls)
collisions with walls
idea of collisions causing force
(b) P = F / A in any form words or numbers
0.59
\(N / cm^2\)
(c)(i) (Area = π × \(r^2\) =) 50.2654 (\(cm^2\))
(c)(ii) smaller area (in contact with the table)