A-level Physics JAN 2018 GUNPOWDER energy mechanics question help !!!!
Hey I've been stuck with this question about energy from the January 2018 edexcel unit 1, and I'd be REALLY grateful if someone could help solve this question ASAP :
"It can be assumed that only 50% of the energy supplied by the gunpowder in the cannon would have been transferred to the capsule.
Determine the mass of gunpowder that would have been required to obtain a maximum speed of 11km/s.
mass of capsule = 1500 kg
energy released from gunpowder = 3 MJ / kg"
THANK YOU SO MUCH
"It can be assumed that only 50% of the energy supplied by the gunpowder in the cannon would have been transferred to the capsule.
Determine the mass of gunpowder that would have been required to obtain a maximum speed of 11km/s.
mass of capsule = 1500 kg
energy released from gunpowder = 3 MJ / kg"
THANK YOU SO MUCH
Original post by bobjard
Hey I've been stuck with this question about energy from the January 2018 edexcel unit 1, and I'd be REALLY grateful if someone could help solve this question ASAP :
"It can be assumed that only 50% of the energy supplied by the gunpowder in the cannon would have been transferred to the capsule.
Determine the mass of gunpowder that would have been required to obtain a maximum speed of 11km/s.
mass of capsule = 1500 kg
energy released from gunpowder = 3 MJ / kg"
THANK YOU SO MUCH
"It can be assumed that only 50% of the energy supplied by the gunpowder in the cannon would have been transferred to the capsule.
Determine the mass of gunpowder that would have been required to obtain a maximum speed of 11km/s.
mass of capsule = 1500 kg
energy released from gunpowder = 3 MJ / kg"
THANK YOU SO MUCH
Convert the velocity to m/s:
11 km/s = 11x103 m/s
Then find the kinetic energy of the moving capsule:
KE = (mv2)/2 = 1500 x (11,000)2 / 2 = 9.075x1010 joules
This is the energy that must delivered by the gunpowder to the capsule.
The gunpowder energy yield is:
Egun = efficiency x yield x mass
and
Egun = KE (assuming energy transfer is 100%)
rearranging for mass as the unknown variable:
massgunpowder = KE / (efficiency x yield)
mass = 9.075x1010 / (0.5 x 3x106)
Gunpowder mass = 60.5x103 kg = 60.5 metric tonnes
A 1.5 tonne capsule travelling at 11km/s (approximately the escape velocity to leave Earth orbit) needs an enormous amount of energy to achieve that speed. To give a comparison, the Dawn space probe to study the asteroids Vesta and Ceres in the asteroid belt between Mars and Jupiter, had a payload mass of 1.2 tonnes.
The rocket launcher for the probe was the Delta II system, which had a launch mass of around 230 tonnes and most of that was fuel. It stood around 40 metres tall.
https://en.wikipedia.org/wiki/Delta_II
[video="youtube;ncLLVj1qMC8"]https://www.youtube.com/watch?v=ncLLVj1qMC8[/video]
(edited 6 years ago)
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