A fireworks display uses a launcher containing a small amount of gunpowder. Fig. 1 shows a simplified firework before launch. When the fuse burns, hot gases...
Question 1 Report
A fireworks display uses a launcher containing a small amount of gunpowder. Fig. 1 shows a simplified firework before launch. When the fuse burns, hot gases form quickly and push the firework upwards. The casing later breaks open high in the air and coloured light is seen. The display team keeps spectators at a safe distance because the gases exert a large force on the firework and hot particles can cause burns. The diagram shows the launch direction.
(a) What causes the large pressure inside the casing? [1]
(b) When the firework rises, which energy store increases? [1]
A safety valve is fitted to a compressed-air cylinder in a diving centre. Fig. 1 shows the valve as a simple cross-section. If the air pressure becomes too large, the gas pushes a spring-loaded cap upwards and air escapes. The cap then returns when the pressure falls. The engineer checks that the valve is not blocked before filling cylinders. Gas particles collide with every surface inside the cylinder, including the cap. The diagram shows the direction in which the cap can move.
(a) What causes the gas pressure on the cap? [1]
(b) When the cap rises, which way is the force from the gas acting? [1]
Answer Details
Firework
- (a) The large pressure is caused by more frequent or more energetic collisions of hot gas particles with the casing [1].
- (b) As the firework rises, its gravitational potential energy store increases [1].
Compressed-air safety valve
- (a) Pressure on the cap is caused by collisions of gas particles with the cap [1].
- (b) When the cap rises, the force from the gas acts upwards or outwards [1].
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