21. Blood flows at an average speed of \( 0.40 \mathrm{~m} / \mathrm{s} \) in a horizontal artery of radius 1.0 cm . The average pressure is \( 1.4 \times 10^{4} \mathrm{~N} / \mathrm{m}^{2} \) above atmospheric pressure (the gauge pressure). (a) What is the average speed of the blood past a constriction where the radius of the opening is 0.30 cm ? (b) What is the gauge pressure of the blood as it moves past the constriction?

14. A train moving at an average speed of \( 72 \mathrm{~km} / \mathrm{h} \) takes 15 seconds to completely cross a bridge that is 80 metres long (a) Express \( 72 \mathrm{~km} / \mathrm{h} \) in metres per second (b) Find the length of the train in metres ( 2 mk )

Problem (1) uniform bar \( A B \) of mass 40 kg and 8 m length is fixed in a vertical plane by two strings \( A D \) Id \( B H \), and a body of mass 60 kg is humg at a point \( C \) on \( A B \) so the bar became in an quilibrium state horizontally, and \( m(\angle D A B)=120^{\circ}, m(<H B A)=150^{\circ} \). find the magnitude fine tension in each of the strings and the length \( \overline{A C} \). Answer.

Sebuah mobil bermassa 1200 kg bergerak dengan kecepatan \( 20 \mathrm{~m} / \mathrm{s} \). Mobil tersebut kemudian direm hingga berhenti setelah menempuh jarak 50 meter. Berapakah gaya pengereman yang bekerja pada mobil tersebut?

Problem (2) \( A \) iniform ladder \( A B \) of weight 10 kg .w and 3 m length rests with its end \( A \) on a smooth horizomal noor and is end B on a smooth vertical wall. the ladder is kept in equilibritum by a rope tied to on of irs ends A. and irs other end is attached to a point on the hori=ontal plane vertically below B. if the ladder is inclined at \( +5^{\circ} \) to the horizontal, a man of weight 60 kg . w was ascending the ladder find the magnitude of the tension in the rope when the man is \( 2 m \) away from \( A \) \( \qquad \) \( \qquad \)

A 1 km long goods train is running at a speed of 45 \( \mathrm{~km} / \mathrm{h} \). The time taken by this goods train to pass through a 2 km long tunnel is: \( \begin{array}{ll}\text { (A) } 1 \text { minute } & \text { (B) } 2 \text { minutes } \\ \text { (C) } 3 \text { minutes } & \text { (D) } 4 \text { minutes }\end{array} \)