Question:
How is the work-energy theorem demonstrated in thsi video?
Answer:
The kinetic energy is transferred to the “bullet” when the blowing force F does positive work W on the “bullet”.
According to the work-energy theorem, the amount of work done W (and thus the KE gained by the bullet) is given by the formula
W=F.d
where d is the distance through which the force is applied.
In this demonstration, d corresponds to the length of the blow pipe.
Delving Deeper
Size does matter, when it comes to projectile weapons. The longer distance allows more work done, and results in higher KE of the projectiles. This explains why long bows have longer range than crossbows, rifles have longer range than pistols, and cannons have longer range than mortars.
xmPhysics 