1.A large crate is placed on the bed of a turck without being tied to the truck.
ID: 1685551 • Letter: 1
Question
1.A large crate is placed on the bed of a turck without being tied to the truck. The turck accelerates forward and the crates remains at rest relative to the truck, what force does cause the crate to accelerate?2.It is an established fact that sports utility vehicles (suv) are more susceptible to tip over in an accident than small passenger cars, what does cause the suv to tiop over and what can be done ( in future design) to keep this from happening?
3.A platoon of soldiers marches in step along a road, why are they ordered to break step when they are crossing a bridge?
Explanation / Answer
1) Friction. In this instance, this is the only force which can cause the crate to accelerate and remain in the rest frame of the truck. 2) High center of gravity, or more properly, a high center of mass. Because the center of mass is very high (SUV's have a lot of heavy metal in roofs, and the chassis's are higher than typical cars), the SUV therefore has a less stable equilibrium. --- Torque is defined as time rate of change in angular momentum. For zero torque, the SUV will not roll. A non-zero torque is required to roll a vehicle. Torque is defined as the cross product between a position vector and a force. This force is namely the force applied to the center of mass, and a vehicle with a higher center of mass will experience a greater rolling torque, causing it to more easily lose its metastable equilibrium and experience a change in angular momentum and roll. 3) Resonant Frequency. It is an observed phenomenon of physics that the resonant frequency will provide the greatest oscillations possible for a given system. If all of the soldiers walk in step, there is a chance they might produce a resonant frequency, namely, a vibrational frequency equal to the natural frequency of the bridge. If this occurs, it is possible that the bridge may collapse (enough soldiers, and enough weight, all marching in step at the resonant frequency of a bridge can bring a bridge down). To avoid this, all the soldiers have to do is walk across the bridge one-at-a-time, or, more conveniently, simply walk out of step (to save time).
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