13-Work and Energy1-Work, Power, and Machines Work: The transfer of energy to an Object by the application of force thatCauses the object to move in the Direction of the force. Work = force * distance w = F * dUnit of work: work is measured in Joule Work zero when object is not moving on applying force. Work is zero when force is not applied even if an object is moving certain distance.

Math skills- workA crane uses an average force of 5200 N to lift a girder 25 m. How much work does the crane do on the girder?Given: F = 5200 N, distance (d) = 25 m.Write the required equation, W = F x dInsert the known values and solve.w = 5200 N x 25m = 130,000 N.m

W=F x dF = W/dd = W/F

Math skills-WorkA mechanic uses a hydraulic lift to raise a 1,200 kg car 0.50 m off the ground. How much work does the lift do on the car?Given: mass of car=1200 kg, convert into weight. Weight = mass x g (constant value) Weight = m x g(9.8m/s2)=1200 kg x 9.8 m/s2 = 17760 kg.m/s2The value of weight is equal to the amount of force. Therefore, W = F x dW = 17760 N X 0.50m = 88830 N.m

PowerPower: A quantity that measures therate at which work is done or energyis transformed. In other words. How much work is done in a given amount of time. Equation: Power = work/time, p = w/tPower is measured in unit - watts Watt is a SI-unit. One watt equals one joule of work is done in one second. 1watt = 1 j/sAnother unit is : Horse power One horse power is equal to 746 watts. As you might have guessed, one horse power was originally the average power output of a horse.

Math skills: Powerp = W/tW = p . tt = W/pLisa walks up the stairs on her way to class. She weighs 565 N, and the stairs go up 3.25 m vertically. If Lisa climbs the stairs in 12.6 s, what is her power output? and If time is 10.6 s ? Given: F = 565 N, d = 3.25 m, t =12.6 s and 10.6 sWrite required equation: p = W/t but W = F.dInsert the known values and solve.p = F*d/t = 565 N*3.25 m/12.6 s = N.m/s

p = F*d/t = 565 N*3.25 m/10.6 s = N.m/s

Machines & Mechanical AdvantageMachine; A device with moving parts that work together to accomplish a task. Example: a bicycleAll parts of bicycle work together to transform forces from muscles to speed and motion.Machines make work easier by increasing the input force,& changing the direction of force.

Mechanical AdvantageMechanical Advantage: It is defined as the ratio between the output force and input force, it is also equal to the ratio between the input distance and the output distance if friction is ignored. Equation formula to calculate MA is,MA =Output force/input forceMA = Input distance/output distanceMA = FO/Fi and MA = di/do

Input force: The force you apply on machineOutput force: The force that machines apply for you.

Math skills: calculate-MA Calculate the MA of a ramp that is 5.0 m long and 1.5 m high. MA = di/do di=MA * doGiven: Input distance=5.0 m, do=di/MA Output distance=1.5 m MA = input distance/output distance = 5.0 m/1.5 m = 3.3Mechanical advantage has no unit, because the similar units cancelled out. It is simply a numeric number.MA = Fo/FiFi = Fo/MAFo = Ma * Fi

Math skills: Alex pulls on the handle of a claw hammer with a force of 15 N. If the hammer has a mechanical advantage of 5.2, how much force is exerted on the nail in the claw?Given: input force Fi=15 N, MA = 5.2, Fo = ?Required equation is, Fo= MA * FiInsert the values and solve. Output force = 5.2 * 15 N = 78 NFor more practice, visit go.hrw.com and enter Keyword HK8MP

Home workPage # 432 do practice problems 2,3Page # 434 do practice problems 1Solve all problems from given work sheetPage 437 Section 1- reviewAnswer 1 t0 4 and math skills, solve problems 5 to 8