A1050 kg automobile is at rest at a traffic signal. at the instant the light turns green, the automobile starts to move with a constant acceleration of 3.3 m/s2. at the same instant a 2350 kg truck, traveling at a constant speed of 8.6 m/s, overtakes and passes the automobile.
(a) how far is the center of mass of the automobile-truck system from the traffic light at t = 2.1 s?
(b) what is the speed of the center of mass of the automobile-truck system then?

Two conductors, a and b, are each in the shape of a tetrahedron. but of different sizes. they are charged in the following manner: 1. tetrahedron a is charged from an electrostatic generator to charge q. 2. tetrahedron a is briefly touched to tetrahedron b. 3. steps 1 and 2 are repeated until the charge on tetrahedron b reaches a maximum value. if the charge on tetrahedron b was q/4 after the first time it touched tetrahedron a. what is the final charge qbmax on tetrahedron b?