Đề thi ngày 28/5/2019: Hot air balloon

The diagram illustrates the working of a hot air balloon. Overall, it is clear that the envelope is the largest part of the total area. In addition, the diagram indicates that propane is the fuel that is used to produce the hot air.

At the base of the hot air balloon, a propane cylinder is located in the basket. The propane then mixes with air in the burner, producing a flame to heat the air. Next, the hot air rises inside the envelope, causing the balloon to rise from the ground, because the hot air is lighter than the cool air in the surrounding atmosphere. Ropes are shown securing the basket section to the skirt of the envelope.

In addition to the skirt at the base of the envelope, gores and panels also form part of the envelope section. A parachute valve at the top of the envelope is a self-sealing flap. This allows the pilot of the balloon to control the rate at which the hot air can escape.

(178 words, Band 8.0+)

Nguồn: IELTS Ngọc Bách