英语阅读给个标准答案If a mother pushes her small son in a swing,giving

英语阅读给个标准答案
If a mother pushes her small son in a swing,giving only a light force each time he returns,eventually he will be swinging quite high.The child can do this for himself by using his legs to increase the motion,but both the mother's push and the child's leg movements must occur at the proper moment,or the extent of the swing will not increase.In physics,increasing the swing is increasing the amplitude; the length of the rope on the swing determines its natural oscillation period.This ability of an object to move periodically or to vibrate when stimulated by a force operating in its natural period is called resonance.
Resonance is observed many times without consciously thinking about it; for example,one may find an annoying vibration or shimmy in an automobile,caused by a loose engine mount vibrating with increasing amplitude because of an out-of-round tire.The bulge on the tire slaps the pavement with each revolution; at the natural resonance point~of the engine mount,it will begin to vibrate.Such vibrations can result in considerable damage if allowed to persist.Anther destructive example of resonance is the shattering of a crystal goblet by the production of a musical tone at the natural resonant point of the goblet.The energy of the sound waves causes vibration in the glass; as its amplitude increases,the motion in the glass exceeds the elasticity of the goblet,and it shatters.
An instrument called a tachometer makes use of the principle of resonance.It consists of many tiny bars,loosely fastened together and arranged so that each bar can slide independently of the others.Movement of the bars causes changes in a dial.When placed next to a rotating motor or engine,the tachometer picks up slight vibrations which are transferred to the resonant bars.These bars begin to move,and the resulting dial may be read to find the revolutions per minute of the motor very quickly.
74.An object,if moving rhythmically when stimulated in a natural period,is said to
A.vibrate.B.resonate.C.swing.D.oscillate.
75.The distance a swing moves from its resting position is called its
A.revolution.B.movement.C.frequency.D.amplitude.
76.A tachometer is an instrument that uses resonance to determine
A.the speed of a motor in revolutions.B.the frequency at which a motor vibrates.
C.the amplitude of an engine that oscillates.D.the changes in a dial within a car engine.
77.An annoying vibration can be caused at the natural resonance of the car's engine mount
A.if the engine moves too fast.B.if the engine's amplitude increases.C.if a tire gets out of balance.D.if a damage occurs in the engine.
78.In which of the following cases is it useful to consider the relationship between the length of an oscillating object and its natural period?
A.Adjusting the speed of a car.B.Adjusting a clock pendulum.C.Adjusting tire balance.D.Adjusting engine mounts

B,D,D,B,B
第一问题请看这句话：This ability of an object to move periodically or to vibrate when stimulated by a force operating in its natural period is called resonance.
第二个问题：基本常识,肯定是振幅 amplitude
第三个问题：汽车上的转速计肯定是利用共振原理来决定表盘的读数的.
第四个问题：紧贴文章主题,选B
第五个问题：B,钟摆原理应该知道,我们调表不就是用的这个原理吗?