A model rocket is constructed with a motor that can provide a total impulse of 3

Question

A model rocket is constructed with a motor that can provide a total impulse of 33.0 N·s. The mass of the rocket is 0.104 kg. What is the speed that this rocket achieves when it is launched from rest? Neglect the effects of gravity and air resistance.

A water slide is constructed so that swimmers, starting from rest at the top of the slide, leave the end of the slide traveling horizontally. As the drawing shows, one person hits the water 5.00 m from the end of the slide in a time of 0.712 s after leaving the slide. Ignore friction and air resistance, find the height H in the drawing.

Explanation / Answer

from the impulse momentum theorem

impulse = m( vf- vi)

33 Ns = 0.104 kg ( vf- 0)

vf = 317.3 m/s

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final speed of the swimmer is

vf = del x/ t = 5.0 m/0.712 = 7.0 m/s

Apply kinematic equation

-h =- 1/2 * g t^2 = 1/2 * 9.8 ( 0.712)^2 = 2.48 m

from the conservation of energy

1/2 * mv^2 = mg(H-h)

H = h+ v^2/2g = 2.48 m + ( 7)^2/2 ( 9.8) = 4.98 m

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