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Impulse and Momentum

Impulse and Momentum. Terminology. Impulse: F Δ t, or the product of the average force on object and the time interval over which it acts (measures in Newton-seconds) Momentum: mv, or the product of the object’s mass and the objects velocity

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Impulse and Momentum

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  1. Impulse and Momentum

  2. Terminology • Impulse: FΔt, or the product of the average force on object and the time interval over which it acts (measures in Newton-seconds) • Momentum: mv, or the product of the object’s mass and the objects velocity • Impulse-momentum Theorem: FΔt= pf –pi ; The impulse on an object is equal to the object’s final momentum mines the object’s initial momentum (p= momentum)

  3. Concepts • The momentum of an object is the product of its mass and velocity and is a vector quantitiy. • The impulse of an object is the average net force exerts on the object multiplied by the time interval over which the force acts. • The impulse on an object is equal to the change in momentum of the object.

  4. Questions • A pitcher claims he can throw a 0.151 kg baseball with as much momentum as a 3.0 g bullet moving with a speed of 1.50  103 m/s. Which of the following is true • a) ball has greater kinetic energy. • b) both have the same kinetic energy.     • c) the bullet has greater kinetic energy. • None of the above • A pitcher throws a 0.15 kg baseball so that it crosses home plate horizontally with a speed of 10 m/s. It is hit straight back at the pitcher with a final speed of 24 m/s. Assume the direction of the initial motion of the baseball to be positive. • What is the impulse delivered to the ball? • Find the average force exerted by the bat on the ball if the two are in contact for 2.0  10-3 s.

  5. Equations • F=MA • F=M (ΔV/ ΔT) • P=MV • FΔt= MΔV • P= momentum • V=veolicity • M= mass • F= force • T= time

  6. Conservation of Linear Momentum in Collisions

  7. Terminology • Closed system: a system that does not gain or lose mass • Isolated system: a closed system on which the net external force is zero • Law of conservation of momentum: states that the momentum of any closed, isolated system does not change

  8. Concepts and Equations • In a linear collision, momentum is neither gained nor loss. Momentum is transferred to another object. • ½m1iv1i² + ½m2iv2i²= ½m1fv1f² + ½m2fv2f² • m1v1i + m2v2i= m1v1f + m2v2f • m1v1i + m2iv2i= vf (m1+ m2)

  9. Quesions • A 1245 kg car traveling initially with a speed of 25.0 m/s in an easterly direction crashes into the rear end of a 9100 kg truck moving in the same direction at 20.0 m/s. The velocity of the car right after the collision is 18.0 m/s to the east. • What is the velocity of the truck right after the collision? • In a football game, a receiver is standing still, having just caught a pass. Before he can move, a tackler, running at a velocity of +4.8 m/s, grabs him. The tackler holds onto the receiver, and the two move off together with a velocity of +2.6 m/s. The mass of the tackler is 116 kg. Assuming that momentum is conserved, find the mass of the receiver.  • A) 121 kg • B)107 kg • C) 73 kg • D) 98 kg

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