CBSE Pathshala

IX Term -1 Solved numerical Gravitation and Laws of motion Q.A rifle of mass 3 kg fires a bullet of mass 0.03 kg. The bullet leaves the barrel of the rifle at a velocity of 100 m/s. If the bullet takes 0.003 s to move through its barrel, calculate the force experienced by the rifle due to the recoil. Ans:    Mass of the rifle (m1)   = 3 kg    Mass of the bullet (m2)   = 0.03 kg Initial velocity of the rifle (u1) = u2   = 0,   Final velocity of the rifle (v1) = ? Final velocity of the bullet (v2) = 100 m s-1 According to law of conservation of momentum = m1u1   + m2u2   = m1v1   + m2v2    Using the law of conservation of momentum,  0 + 0 = 3v1   + 0.03 x 100 =-1m/s   Negative sign shows that the rifle moves in a direction opposite to that of the bullet, Force experienced by the rifle due to its recoil= m1v1/t =(3x-1)/0.003=-1000N   Ther...

9th physics: Force and laws of Motion An object of mass 2 kg is sliding with a constant velocity of 4 m/ s   on a frictionless horizontal table. The force required to keep the object moving with the same velocity is (a) 32 N                                    (b) 0 N                          (c) 2 N                          (d) 8 N                          (b]         Rocket works on the principle of conservation of (a) mass...