2. Aball is thrown upward with a speed of \( 19.6 \mathrm{~m} / \mathrm{s} \). a. How high doesit go until its upward speed decreases to zero. b. How long does the ball take in this upward trip? \( c \). How long does the ball take to return to the initial position? \( d \). What will be its velocity then

La cantidad de un material radiactivo disminuye a la mitad cada 10 años. Si comenzamos con 80 gramos, ¿cuánto quedará después de 30 años?

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: \( \begin{array}{ll}\text { (A) } 1 \text { minute } & \text { (B) } 2 \text { minutes } \\ \text { (C) } 3 \text { minutes } & \text { (D) } 4 \text { minutes }\end{array} \)

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 \( A \) \( \qquad \) \( \qquad \)

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 )

Question ix. An ideal gas is enclosed in a cylinder which has a movable piston. The gas is heated, resulting in an increase in temperature of the gas, and work is done by the gas on the piston so that the presure remains constant. a) Is the work done by the gas negative, positive or zero? b) From a microscopic view, how is the internal energy of the gas molecules affected? c) Is the heat less than, greater than or equal to the work? Explain you answer.