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Adv Physics

Adv Physics. Chapter 5 Sections 1 & 3. Work. Force applied over a given distance If force is constant and body moves in a straight line W = F Δx where W = work (scalar quantity) F = force in direction of motion Δx = distance moved and [W] = Nm = Joule, J

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Adv Physics

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  1. Adv Physics Chapter 5 Sections 1 & 3

  2. Work • Force applied over a given distance • If force is constant and body moves in a straight line W = F Δx where W = work (scalar quantity) F = force in direction of motion Δx = distance moved and [W] = Nm = Joule, J = ft lb

  3. Sample Problem Compute the work required to lift a 1 kg mass to a height of 5 m if it doesn’t accelerate.

  4. Sample Problem Compute the work required to lower a 1 kg mass a distance of 5 m if it doesn’t accelerate.

  5. Work cont’d. • Work is positive if the force and motion are in the same direction • Work is negative if the force and motion are in opposite directions • Net work – sum of the work done by all the forces acting on an object, ΣW

  6. Sample Problem Compute the net work done in raising the 1 kg mass 5 m and then returning it to its initial position.

  7. Sample Problem Compute the work required to slide a 1 kg mass at constant speed along a horizontal surface having a coefficient of kinetic friction of 0.3 for a distance of 5 m.

  8. Sample Problem A girl pulls a wagon with constant velocity along a level path for a distance of 45 m. The handle of the wagon makes an angle of 20 degrees with the horizontal and she exerts a force of 85 N on the handle. Find the amount of work the girl does in pulling the wagon.

  9. Energy • Having the ability to do work • Kinetic energy – energy due to motion KE = ½ m v2 where KE = kinetic energy (scalar quantity) m = mass v = speed [KE] = J

  10. Sample Problem A baseball has a mass of 0.14 kg and is thrown with a speed of 26 m/s. What is its kinetic energy?

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