1. A 1500kg automobile starts from rest on a horizontal road and gains speed of 72km/h in 30 s.
a) What is the average power required of the car at the end of the 30 s?
b) What is the average power required of the car during the 30 s interval?
c) What is the instantaneous power at the end of the 30 s interval, assuming that the acceleration is constant?
2.A vessel at rest explodes, breaking into three pieces. Two pieces, having equal mass, fly off perpendicular to one another with the same speed of 30 m/s. The third piece has three times the mass of each other piece. What are the magnitude and direction of its velocity immediately after the explosion?
3. An object is tracked by a radar station and found to have a position vector given by
r(vector) = (3500 - 160t)i + 2700j + 300k,
with r(vector) in meters and t in seconds. The radar station's x-axis points east, its y-axis north, and its z-axis vertically up. If the object is a 250kg meteorological missile, what are:
a) Its linear momentum
b) Its direction of motion
c) The net force on it
1. (a) It is nonsense to ask "average" something at instantaneous time because "average" must involve a time interval.
(b) For the average power during a 30 s interval, P=F*v. Assume the acceleration is constant, F is constant and v is the average velocity ...
This response shows how to calculate power using formula, as well as mentioning conservation of momentum and direction of momentum to solve the equations.