A rifle with a weight of 35 N fires a 4.5 g bullet with a speed of 240 m/s. a)fi

Question

A rifle with a weight of 35 N fires a 4.5 g bullet with a speed of 240 m/s.

a)find the recoil speed of the gun in m/s
b)If a 650 N man holds the rifle firmly against his shoulder, find the recoil speed of the man and rifle in m/s.

A 715 N man stands in the middle of a frozen pond of radius 4.0 m. He is unable to get to the other side because of a lack of friction between his shoes and the ice. To overcome this difficulty, he throws his 1.2 kg physics textbook horizontally toward the north shore at a speed of 4.0 m/s. How long does it take him to reach the south shore? (in seconds)

A 75.0 kg ice skater moving at 9.00 m/s crashes into a stationary skater of equal mass. After the collision, the two skaters move as a unit at 4.50 m/s. If the impact time is 0.115 s, what are the magnitudes of the average forces experienced by each skater during the collision?

Force experience by moving skater in N.

Force experience by stationary skater in N.

Explanation / Answer

(a)The weight of rifle = 35 N
    The mass of rifle,M = 35 / 9.8 = 3.6 kg    The recoil speed of rifle = u
   The mass of bullet,m = 4.5 g = 4.5 x 10-3 kg    The speed of bullet, v = 240 m/s    According to law of conservation of momentum    net momentum = 0    Mu + mv = 0    u = (- mv) / M    u = (- 4.5 x 10-3 x 240) / 3.6    u = - 0.3 m/s    So the recoil velocity of rifle, u = - 0.3 m/s    The negative sign is due to opposite direction.    (b) The mass of man is 650 N    Then the recoil velocity is, u = (- mv) / (M+650)                                            u = (- 4.5 x 10-3 x 240) / (3.6+650)                                            u = 1.65 x 10-3 m/s

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