A block of mass M and a block of mass 3M are connected by a string, as shown above. The blocks are held with the string horizontally and are released from rest at the same time from a height H above the ground. How does the acceleration of the center of mass of the system compare to the acceleration of the object of mass M ?

One hazard of space travel is debris left by previous missions. there are several thousand masses large enough to detect by radar orbiting the earth, but there are far greater numbers of very small masses such as flakes of paint. calculate the force exerted by a 0.110 mg chip of paint that strikes a space shuttle window at a relative speed of 5.00 ✕ 103 m/s and sticks, given the collision lasts 6.00 ✕ 10-8 s. such a collision chipped the window of the ill-fated challenger in june 1983, causing $50,000 of damage.