An object of mass 3.1 kg is projected into the air at a 45° angle. It hits the ground 3.9 s later. What is its?
An object of mass 3.1 kg is projected into the air at a 45° angle. It hits the ground 3.9 s later. What is its change in momentum while it is in the air? Ignore air resistance.
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As the horizontal velocity is constant (no air resistance) .. the change in momentum is due to the change in vertical velocity.
When u = initial vertical velocity, the velocity change is -2u (positive direction upward)
Vertical motion for whole journey .. [applying v = u +at .. vertically]
Initial vel u, final vel -u, t = 3.90s, g = -9.80 m/s² ..
-u = u - gt
2u = gt .. .. 9.80 x 3.90 .. 2u = - 38.22 m/s
Change in vertical momentum = m x -2u .. .. 3.10kg x -38.22m/s .. .. ►118.48 kg.m/s