求英文物理答案解答?

[匿名]

2015-11-09 9:59 am

two particles are launched from the origin of the coordinate system at time t = 0. Particle 1 of mass m1 = 4.30 g is shot directly along the x axis (on a frictionless floor), where it moves with a constant speed of 12.6 m/s. Particle 2 of mass m2 = 3.90 g is shot with a velocity of magnitude 24.9 m/s, at an upward angle such that it always stays directly above particle 1 during its flight. (a) What is the maximum height Hmax reached by the com of the two-particle system? In unit-vector notation, what are the (b) velocity and (c) acceleration of the com when the com reaches Hmax?

回答 (1)

麻辣

2015-11-09 8:59 pm

(a) What is the max height Hmax=? reached by the com of the bothparticle systems in unit-vector notation ?

The 1st particla is x-axis:

v = 12.6i

x = 12.6t

a = 0

The 2nd particle is parabola curve:

Vx = 24.9*cosQ = 12.6

cosQ = 12.6/24.9 = 0.506

Q = acos(0.506) = 59.60 degrees

Vy = 24.9*sin59.60 - 9.8t = 21.5 - 9.8t = 0

t = 24.9*0.8625/9.8 = 2.19 sec

X = 12.6t

Y = 21.5t - 0.5*9.8t^2

Hmax = Y(2.19)

= 21.5*2.19 - 0.5*9.8*2.19^2

= 46.82 meters

(b) what are the velocity

The 1st particle: v = 12.6i

The 2nd particle:

Vx = 12.6i

Vy = 0j

(c) acceleration of the com when the com reaches Hmax ?

The 1st particle: a = 0

The 2nd particle: a = -gj = -9.8j

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