27. Two trains, 1 and 2 , have an equal mass of \( m=5,000 \mathrm{~kg} \) each. Train 1 is traveling with a speed \( n=15 \mathrm{~m} / \mathrm{s} \) before striking train 2 , which was at rest. If the two trains lock together as the result of the collision. What is their common speed immediately after collision?

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? \( \begin{array}{lllll}\text { A) } 0.25 & \text { B) } 2.5 \mathrm{~cm} & \text { C) } 12.5 \mathrm{~cm} & \text { D) } 25 \mathrm{~cm} & \text { E) } 1.25\end{array} \)

(c) Vektor kedudukan sebuah dron \( A, I \) saat selepas meninggalkan tempat berlepas ialah \( t\left(\frac{30}{15}\right) \) manakala vektor kedudukan dron \( B \) ialah \( \left(\frac{50}{5}\right)+t\left(\frac{10}{10}\right) \). 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 afler leaving the takeoff point is \( t\left(\frac{30}{15}\right) \) while the position vector of drone B is \( \left(\frac{50}{5}\right)+t\left(\frac{10}{10}\right) \). Determine the velocity of drone \( A \) and drone B. Will drone \( A \) and drone B collide? [3 markah/marks]

A 10 kg crate is placed on a rough horizontal surface \( \mu_{\mathrm{k}}=0.4 \) and connected with 12 kg hanging mass via a string that passes over a massless and frictionless pully as shown in the figure beside. Thé mass ( kg ) that must be added to the crate so that the crate moves with constant velocity is:

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:

(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? \( \begin{array}{llll}\text { A) } 185 \mathrm{~J} & \text { B) } 433 \mathrm{~J} & \text { C) } 575 \mathrm{~J} & \text { (D) } 720 \mathrm{~J}\end{array} \)