# A piece of wood of mass 0.03 kg is dropped from the top of a mass 0.02 kg is fired vertically upward, with a velocity 100 , from the ground. The bullet gets embedded in the wood. Then the maximum height to which the combined system reaches above the top of the building before falling below is : (g=10 ) (a) 30m (b) 10m (c) 40m (d) 20m

## Question ID - 50231 :- A piece of wood of mass 0.03 kg is dropped from the top of a mass 0.02 kg is fired vertically upward, with a velocity 100 , from the ground. The bullet gets embedded in the wood. Then the maximum height to which the combined system reaches above the top of the building before falling below is : (g=10 ) (a) 30m (b) 10m (c) 40m (d) 20m

3537

Time taken for the particles to collide,

T= = =1sec

Speed of wood just before collision=gt=10m/s & and speed of bullet just before collision v−gt =100−10=90 m/s

Now, conservation of linear momentum just before and after the collision

(0.02) (1v) + (0.02) (9v)= (0.05)v

⇒150 = 5v

⇒ v = 30m/s

Max. height reached by body h=

h= =45m

Height above tower =40m

Next Question :
 The density of a material in SI units is 128 kg . In certain units in which the unit of length is 25 cm and the unit of mass is 50 g, the numerical value of density of the material is (a) 410 (b) 640 (c) 16 (d) 40