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14 Cards in this Set
- Front
- Back
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momentum
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vector physical quantity describing the quantity of motion
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momentum formula
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P = mv, where P & v both have arrows above them
momentum = mass * velocity = kg * m/s |
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Relationship of P_f to P_i
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In the absence of any external forces, final momentum = initial momentum
momentum is conserved in magnitude & direction |
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Energy
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E
scalar quantity describes the physical state of an object or system of objects |
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Conservation of Energy
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In the absence of external forces, final energy = initial energy
energy can be transformed, never created or destroyed |
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v_i formula
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v_i = X √ ( g / 2H)
initial velocity = horizontal displacement * square root of gravity divided by 2 * the vertical displacement |
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relationship between force & momentum
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F=ma, since a = ∆v / ∆t
F = m * ∆v / ∆t or F = m∆v / ∆t given that P = mv F = ∆P / ∆t |
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momentum of a system with multiple objects
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P_tot = p₁ + p₂ + p₃ + ... + p_n
given that p = mv P_tot = m₁v₁ + m₂v₂ + m₃v₃ + ... + m_n * v_n |
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KE
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kinetic energy
energy describing motion |
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KE formula
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KE = 1/2 mv²
= kg * m² / s² = N·m = J |
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gravitational potential energy
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PE in lab
U_g in lecture and yet other things in the text & lab manual |
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gravitational potential energy formula
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PE = mgh
= mass * gravitational acceleration * vertical displacement displacement below reference level < 0 < displacement above reference level |
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ME
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mechanical energy
ME = KE + PE + U_e mechanical energy is the sum of kinetic energy, gravitational potential energy, and elastic energy |
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formulas for ball & pendulum
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Only KE & PE are present
ME_i = ME_f 1/2 (m₁ + m₂) V_i² + (m₁ + m₂)*g*h_i = 1/2 (m₁ + m₂) V_f² + (m₁ + m₂)*g*h_f Since there is no movement at the final point, simplify to 1/2 (m₁ + m₂) V_i² + (m₁ + m₂)*g*h_i = (m₁ + m₂)*g*h_f since all terms have m₁ + m₂, divide by that & simplify 1/2 V_i² + g*h_i = g*h_f, then solve for V_i² 1/2 V_i² = g*h_f - g*h_i, factor out g 1/2 V_i² = g (h_f - h_i) 1/2 V_i² = g∆h, assume that ∆h = h 1/2 V_i² = gh V_i² = 2gh V_i = √ (2gh) |
