During volcanic eruption chunks of solid rock are blasted out of the volcano. (a) At what initial speed would a volcanic object have to be ejected at 37° to the horizontal from the vent A in order to fall at B as shown in fig. (b) What is the time of flight? (g = 9.8 m/s2)



Correct option is

(255 m/s, 46 s)


Taking the point A as origin, with upward direction of motion positive and using the equation,


For horizontal motion:       x = u cos θ × t                          …(1)

And for vertical motion:    

Substituting t from Eqn.  (1) in (2),


(b) substituting the above value of u in Eqn. (1),




From the top of a tower of a height 40 m, a ball is projected upwards with a speed of 20 m/s at an angle of elevation of 30°. The ratio of the total time taken by the ball to hit the ground to its time of flight (time taken to come back to the same elevation) is (Take g = 10 m/s2)


The maximum height attained by a projectile is increased by 10% by increasing its speed of projection, without changing the angle of projection. The percentage increase in the horizontal range will be


The maximum height attained by a projectile is increased by 10% by changing the angle of projection, without changing the speed of projection. The percentage increase in the time of flight will be


The speed of projection of projectile is increased by 5%, without changing the angle of projection. The percentage increase in the range will be


A projectile has the same range R when the maximum height attained by it is either h1 or h2. Then Rh1 and h2 will be related as


A relief aeroplane is flying at a constant height of 1960 m with speed 600km/hr above the ground towards a point directly over a person struggling in flood water (see fig.). At what angle if sight, should the pilot release a survival kit if it is to reach the person is water? (g = 9.8 m/s2



At a harbour enemy ship is at a distance  from the security cannon having a muzzle velocity of 60 m/s (a) To what angle must the cannon be elevated to hit the ship? (b) What is the time of flight? (c) How far should the ship be moved away from its initial position so that it becomes beyond the range of the cannon? (g = 10 m/s2)


gun, kept on a straight horizontal road, is used to hit a car travelling along the same road away from the gun with a uniform speed of 72 km/hr. The car is at a distance is 500 m from the gun, when the gun is fired at an angle of 45° with the horizontal. Find (a) the distance of the car from the gun when the shell hits it; (b) the speed of projection of the shell from the gun. (g = 9.8 m/s2)



A gun is fired from a moving platform and the ranges of the shot are observed to be R and when platform is moving forward or

backward respectively with velocity V. find the elevation of the gun is


Particles P and Q of mass 20 g and 40g respectively are simultaneously projected from points A and B on the ground. The initial velocities of Pand Q make 45° and 135° angles respectively with the horizontal AB as shown in the figure. Each particle has an initial speed of 49 m/s. The separation AB is 245 m. Both particles travel in the same vertical and plane and undergo a collision. After collision P retraces its path. Determine the position of Q when it hits the ground. How much time after the collision does the particle Q take to reach the ground? (Take g = 9.8 m/s2)