1)A shell is fired from a cannon with a velocity V at an angle θ with the horizontal direction. at
the highest point in it path it explodes into two pieces of equal masses. One of the pieces
retraces its path to the cannon. The speed of the other piece immediately after the
explosion is ????????? Please give the hint to get the answer.
2)In an elastic collision,
a)initial Kinetic energy = final kinetic energy
b)kinetic energy remain constant
does'nt kinetic energy remaining constant means that initial kinetic energy = final kinetic
energy
3)A body has its centre of mass at the origin. the X coordinates of the particles
a)may all be positive
b) may be all non negative
(b) is given correct but not (a). Is'nt all non negative implies they to be positive.
4)A body moving towards a finite body at rest collides with it. It is possible that
a)stationary body remains stationary, the moving object changes its velocity
See in elastic collision there is a case when a body of mass m1 collides with other
body of mass m2 which has much greater mass m1 & is at rest. Here the body of mass m1 after colliding with it start moving in opposite direction with the
same velocity in magnitude, but the direction is changed the mass with m2
remains at rest. And velocity is a vector, doesnt the change in direction means change in
the velocity though not in magnitude but still in direction So isn't option (a) correct
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4 Answers
621)A shell is fired from a cannon with a velocity V at an angle θ with the horizontal direction. at
the highest point in it path it explodes into two pieces of equal masses. One of the pieces
retraces its path to the cannon. The speed of the other piece immediately after the
explosion is ????????? Please give the hint to get the answer.
Here you need to use conservation of momentum at the topmost point..
initial velocity before collision is vcosθ
after collision one part has velocity of -vcosθ
The answer is :::.....
622)In an elastic collision, a)initial Kinetic energy = final kinetic energy
b)kinetic energy remain constant
does'nt kinetic energy remaining constant means that initial kinetic energy = final kinetic energy
No it doesnt ... think of compression during collision ... if that were to happen.. KE would be temporarily stored as potential energy (compression/ spring)
623)A body has its centre of mass at the origin. the X coordinates of the particles
a)may all be positive
b) may be all non negative
(b) is given correct but not (a). Is'nt all non negative implies they to be positive.
All cannot be on one side.. bcos The x coordinate of cm will be greater than 0
