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Các dạng bài tập hay lạ khó chương DAO ĐỘNG CƠ HỌC có lời giải chi tiết

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2<br />

kS<br />

13,95 W<br />

W 14, 4( mJ )<br />

2<br />

2<br />

2 2 kS<br />

kx<br />

4. kS<br />

0,45( mJ )<br />

Wd<br />

W 12,6 W<br />

2<br />

2 2<br />

2<br />

9. kS<br />

Wd<br />

W 14, 4 9.0,45 10,35( mJ )<br />

2<br />

Ch n C.<br />

Câu 42.<br />

2 2<br />

kS<br />

kA<br />

2 8 W W 9( mJ )<br />

kx 2 2<br />

Wd<br />

W S<br />

4. kS kS<br />

5 W<br />

1( mJ )<br />

2 2<br />

2 2<br />

2 3<br />

A<br />

ng 3,5S = A + A/6 thì v l n c :<br />

x A<br />

Câu 43.<br />

<strong>Các</strong>h 1:<br />

A 5A<br />

6 6<br />

2 2 2<br />

kx kA 25 kA 11<br />

Wd<br />

W W 2,75( J ) Ch n C.<br />

2 2 36 2 36<br />

Theo <strong>bài</strong> ra: t 1 = t 2 = t mà<br />

t<br />

t<br />

1<br />

2<br />

1 x arccos<br />

1<br />

A<br />

1 x2 1 x1<br />

arccos arccos<br />

A A<br />

nên:<br />

x1 x2 x1<br />

arccos arccos arccos<br />

A A A<br />

x1 1 1 3<br />

cos arccos<br />

A 2 8 4<br />

3<br />

4<br />

x1<br />

A<br />

t1<br />

9 16<br />

W W W Wt<br />

1<br />

64( J )<br />

16 9<br />

Ch n l i g c th i gian là x = A/8 và v < 0 thì<br />

cos 2 arccos 1<br />

x A t<br />

T 8<br />

Cho t = 5T/8 thì<br />

2 5T<br />

1<br />

x Acos arccos 0,6132A<br />

T 8 8<br />

2<br />

Wt3 0,6132 W 0,376W Wd<br />

3<br />

0,624W 39,9( J ) Ch n C.<br />

<strong>Các</strong>h 2:

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