oat physics unit 5

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work

product of the magnitude of the displacement and the parallel component of the force.

• W = F_para x d

• F_para = Fcosθ

power

the rate at which work is done or at which energy changes.

• P = E/t = W/t = Fv

• Units: Joules/second (J/s), watts (W), or horsepower (hp)

efficiency of energy

e = W_out / E_in

kinetic energy

the energy a body possesses due to its motion. It depends on the mass and speed of the object.

• KE = ½mv²

work energy theorem

The net work done on an object is equal to the change in kinetic energy.

• W_net = ½mv_f² - ½mv_i²

gravitational potential energy

the energy contained within an object due to its elevation or vertical position.

• Object near surface of Earth: PE = mgh

• Object far from surface of Earth: PE = -GmM/R

  • G = Newton’s gravitational constant

  • M/m = mass of planet and object

  • R = distance from object to center of planet

elastic potential energy

The energy stored by stretching or compressing something.

• U_s = ½kx²

  • k = spring constant

  • x = distance compressed

total mechanical energy

the sum of kinetic and potential energy of a system. TME is constant.

momentum

the quantity of motion that an object has. It is the vector product of mass and velocity.

• p = mv

• F_net = Δp / Δt

conservation of momentum

If the net force in a system is zero, the linear momentum before and after an interaction are equal.

elastic collision

total kinetic energy is conserved after collision.

inelastic collision

total kinetic energy is not conserved after collision (some energy is lost).

• Perfectly inelastic = objects stick together after collision.

impulse

the change in momentum

• I = Δp = F_netΔt

• Area under curve for force vs time

center of mass

The point where all the mass of an object or system of objects is concentrated.

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