1. Un nadador recorre una piscina de largo "L" en 6 s pero si la distancia se duplicara y la rapidez del nadador se triplicara, determine el tiempo utilizado en este caso. \( \begin{array}{lll}\text { a) } 6 s & \text { b) } 8 & \text { c) } 2 \\ \text { d) } 4 & \text { e) } 12 & \end{array} \)

ถ้า \( \overrightarrow{\mathrm{C}}=\overrightarrow{\mathrm{A}}+\overrightarrow{\mathrm{B}}, \overrightarrow{\mathrm{D}}=\overrightarrow{\mathrm{A}}-\overrightarrow{\mathrm{B}} \) และขนาดของ \( \overrightarrow{\mathrm{A}}, \overrightarrow{\mathrm{B}} \) และ \( \overrightarrow{\mathrm{C}} \) มีค่าเท่ากับ 5 นิวตัน, 7 นิวตัน และ 10 นิวตั ตามลำดับ จงหาขนาดของ \( \overrightarrow{\mathrm{D}} \)

19. Ordina Tre automobili accelerano mentre percorrono un tratto rettilineo di strada: auto 1: passa da \( 25 \mathrm{~m} / \mathrm{s} \) a \( 35 \mathrm{~m} / \mathrm{s} \) in 10 s auto 2: passa da 0 a \( 30 \mathrm{~m} / \mathrm{s} \) in 15 s auto 3: passa da \( 32 \mathrm{~m} / \mathrm{s} \) a \( 12 \mathrm{~m} / \mathrm{s} \) in 5 s Ordinale per accelerazione crescente.

(b.) student : (1) My Day 9. An airplane starts from rest and accelerates at a constant rate of \( 3.00 \mathrm{~m} / \mathrm{s}^{2} \) for 30.0 s before leaving the ground. a. How far did it move? b. How fast was it going when it took off? 10. A brick is dropped from a high scaffold. a. What is its velocity after 4.0 s ? b. How far does the brick fall during this time? 11. A tennis ball is thrown straight up with an initial speed of \( 22.5 \mathrm{~m} / \mathrm{s} \). It is caught at the same distance above the ground. a. How high does the ball rise? b. How long does the ball remain in the air?

Arus listrik sebesar 5 mA mengalir pada suatu kawat penghantar selama 0,1 sekon. Berapa besar muatannya ?

\( \left. \begin{array} { c } { L = L _ { 0 } \sqrt { 1 - \frac { v ^ { 2 } } { c ^ { 2 } } } } \\ { = 90 \sqrt { 1 - \frac { ( 0.8 C ) ^ { 2 } } { ( 3 \times 10 ^ { 8 } ) ^ { 2 } } } = 54 m } \end{array} \right. \)