19- A parked ambulance emits a sound of frequency 1200 Hz . What frequency is detected by an observer inside anoth moving with a velocity of \( 72 \mathrm{~km} / \mathrm{h} \). when he move towards the ambulance (speed of sound in air is \( 340 \mathrm{~m} / \mathrm{s} \) ) \( \begin{array}{llll}\text { (i) } 1000 \mathrm{~Hz} & \text { (1) } 1129.4 \mathrm{~Hz} & \text { (1) } 1270.6 \mathrm{~Hz} & \text { (1) } 1700 \mathrm{~Hz}\end{array} \)

Ejemplo 2 Encontremos la velocidad de una bala de 0.02 kg que adquiere una energia cinética de 400 J. \( \begin{array}{lll}\text { Datos: } \\ m=0.02 \mathrm{~kg} & E_{k}=\frac{1}{2} m v^{2} \\ E_{k}=4001 & \frac{2 E_{k}}{m}=v^{2} & \begin{array}{l}\text { Despejamos la velocidad dejándola e } \\ \text { uno de los lados de la ecuación. }\end{array}\end{array} \)

A mass m is traveling at an initial speed \( v_{i}=25.0 \mathrm{~m} / \mathrm{s} \). it is brought to rest in a di ff 62.5 m by a force of 15.0 N . The mass is:

A \( 20-\mathrm{m} \) long steel wire (cross-section \( 1 \mathrm{~cm}^{2} \), Young's modulus \( 2 \times 10^{11} \mathrm{~N} / \mathrm{m}^{2} \) ), is subjecte to a load of \( 25,000 \mathrm{~N} \). How much will the wire stretch under the load? \( \begin{array}{lllll}\text { A) } 0.25 & \text { B) } 2.5 \mathrm{~cm} & \text { C) } 12.5 \mathrm{~cm} & \text { D) } 25 \mathrm{~cm} & \text { E) } 1.25\end{array} \)

(5) Ahmed pulls his little sister Noha in a sled on an iey surface (assume no friction), with a force of 60.0 N at an angle of \( 37.0^{\circ} \) upward from the horizontal. If he pulls her 12.0 m , what is the work done by Ahmed? \( \begin{array}{llll}\text { A) } 185 \mathrm{~J} & \text { B) } 433 \mathrm{~J} & \text { C) } 575 \mathrm{~J} & \text { (D) } 720 \mathrm{~J}\end{array} \)

(c) Vektor kedudukan sebuah dron \( A, t \) saat selepas meninggalkan tempat berlepas ialah \( t\binom{30}{15} \) manakala vektor kedudukan dron \( B \) ialah \( \binom{50}{5}+t\binom{10}{10} \). Tentukan halaju bagi dron \( A \) dan dron \( B \). Adakah dron \( A \) dan dron \( B \) akan bertembung? The position vector of a drone \( A, t \) seconds after leaving the takeoff point is \( t\binom{30}{15} \) while the position vector of drone \( B \) is \( \left(\frac{50}{5}\right)+t\binom{10}{10} \). Determine the velocity of drone \( A \) and drone \( B \). Will drone \( A \) and drone \( B \) collide?