[问答题]
A box rests on the (fr
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i7s6 * un)ar.agi9a 2 scoy*ulof a truck. The truck driver starts the truck and accelerates forward. The box immediately s
)as7* r6lcanui2g.y9 *uoas i tarts to slide toward the rear of the truck bed. Discuss the motion of the box, in terms of Newton’s laws, as seen (a) by Mary standing on the ground beside the truck and (b) by Chris who is riding on the truck
参考答案:
(a) Mary sees the box stay stationary with respect to the ground. There is no horizontal force on
the box since the truck bed is smooth, and so the box cannot accelerate. Thus Mary would describe the motion of the box in terms of Newton’s 1$^{st}$ law – there is no force on the box, so it does not accelerate.
(b) Chris, from his non-inertial reference frame, would say something about the box being
“thrown” backwards in the truck, and perhaps use Newton’s 2$^{nd}$ law to describe the effects of that force. But the source of that force would be impossible to specify.
本题详细解析:
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