Please answer both parts of question 1, as well as question 2. Please provide al
ID: 1600805 • Letter: P
Question
Please answer both parts of question 1, as well as question 2. Please provide all equations that you use as well as the correct final units. Thanks!
1.) With brakes fully applied, a 1260 kg car deccelerates from a speed of 93.0 km/hr.
a.) What is the work done by the braking force in bringing the car to a stop?
b.) What is the change in the kinetic energy of the car?
2.) A constant force of 30.3 N, directed at 27.5o from horizontal, pulls a mass of 12.3 kg horizontally a distance of 3.17 m. Calculate the work done by the force.
Explanation / Answer
1) mass of car M = 1260 kg, speed of car v = 93 km/hr = 93*1000/3600 m/s = 25.83 m/s
intial kinetic energy KE1 = 1/2Mv2 = 0.5*1260*25.83*25.83 = 420437.5 joules
final kinetic energy KE2 = 0
Work done by braking force = change in KE = KE2 - KE1 = 0 - 420437.5 = -420437.5 joules
b) change in KE = 0 - 420437.5 = -420437.5 joules
2) work done W = F.ds i.e. force into distance travelled in direction of force
W = F*s*cos(25) = 30.3*3.17*cos(25) = 86.3 joules