Explosions are rapid burns that break something apart. The amount of volume increases from solids and liquids becoming gases.
"Cannon" Demonstration (01:35)
Burning gun powder creates an expansion of gas that causes a projectile to shoot out of a gun or cannon. A detonator creates a greater force than gunpowder.
Burn Rate (01:33)
Gunpowder blackens a metal plate, but a detonator causes it to explode. The detonator has a much higher burn rate than gunpowder.
Detonators and Shockwaves (02:34)
In a detonator, wires are connected to an electric match which ignites and explodes the charge. The particles are pushed out and collide with surrounding ones.
Shockwaves and Temperature (02:22)
A shockwave compresses air bubbles in the explosive material and rapidly increases the temperature. Increases in pressure cause an increase in temperature.
Effects of Shockwaves (02:15)
Shockwaves from explosions can cause damage to structures and shatter windows miles away. Shockwaves can be useful in mining.
Investigating Materials (03:11)
Demolition experts need to know what it will take to break a material. A tensile stress test reveals what makes a small sample of a material fail.
The Area Under the Curve (01:36)
The area under the curve of a stress/strain graph shows the amount of work and volume needed to break a material.
Brittle materials have a small area under the curve of the stress/strain graph; tough materials have a large area. Materials that have a large plastic section give good warning they might break.
Using Explosives in Mining (01:21)
Mining engineers can set the necessary number of explosives when the know the toughness of the rock. A primer containing a detonator is lowered into a hole filled with gun powder.
Demolition Using Explosives (01:24)
Concrete is weaker in tension and easier to break from the inside. Holes are drilled into concrete and explosives are placed inside.
Credits: Forces, Materials, and Explosions (00:30)
Credits: Forces, Materials, and Explosions
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