Such a cool teacher

Classical Mechanics Level 1

Mr. Andrew excites his students with his home-made cannon demonstration. The 1.27kg cannon is loaded with a 54 grams cricket ball and placed on the ground. Mr. Andrew fires the cannonball horizontally and determines that the cannon recoiled backwards with a speed of 7.8m/s with help of a photogate measurement and asks his students to determine the speed of the ball. So, what is the speed of the ball in m/s?


The answer is 183.44.

Nihar Mahajan by Nihar Mahajan , 20, India

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1 solution

Andrew Ellinor
Jan 29, 2016

It turns out that I keep a cannon like this in the garage just for these purposes.

The momentum of the cannon is 1.27 × 7.8 = 9.906 1.27 \times 7.8 = 9.906 kg m/s. To offset this change in momentum, the cricket ball must have the same momentum in the other direction. The momentum of the cricket ball is 0.054 × v , 0.054 \times v, where v v is our desired velocity.

0.054 v = 9.906 ⟶ v = 183.44 0.054v = 9.906 \longrightarrow v = \boxed{183.44}

3 Helpful 0 Interesting 0 Brilliant 0 Confused

LOL , the teacher only posted the solution :P

Nihar Mahajan - 5 years, 4 months ago

Isn't that 5 significant digits?

Sam Browning - 1 year, 5 months ago

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