Two 50-N weights pull on the scale as shown. The reading on the scale is
1) 0 N.
2) 25 N.
3) 50 N.
4) 100 N.
This is clearer to understand if we think of the situation this way:
5) Since no acceleration is taking place, the forces cancel one another.
6) One of the weights "holds" the scale while the other weight stretches the spring.
7) The two hanging weights provide forces that constitute an action/reaction pair.
Answer: 3, 6
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A source of sound waves is placed at the center of a very large sound-reflecting wall. The source emits 0.500 W of power. Two meters from the source the intensity in W/m2 is
a. 9.95 × 10^?3. b. 1.99 × 10^?2. c. 0.313. d. 0.399. e. 0.625.
A plasma differs from a gas in that
A) its molecules are farther apart. B) it is hotter than a gas. C) it is electrically conducting. D) its atoms are boosted to higher atomic numbers. E) all of the above
The mass of an entire hydrogen atom is converted into energy during the proton-proton chain.
Answer the following statement true (T) or false (F)
A 900-kg car traveling 30.0° south of east at 12.0 m/s collides with a 750-kg car traveling north at 17.0 m/s. The cars stick together. What is the speed of the wreckage just after the collision?
A) 7.21 m/s B) 12.2 m/s C) 20.4 m/s D) 25.0 m/s E) 17.3 m/s