A cannon ball is fired with a muzzle velocity of 300.00 m/sec at an angle of 45⁰ (cont.)?

2020-07-27 12:19 pm
a. What is its maximum horizontal range?
b. Where is the ball after 1.20s?
c. What is its velocity after 2.00s?
d. At what height will it go upward?
e. How long will it stay in the air?

回答 (2)

2020-07-27 1:51 pm
Take g = 9.8 m/s²
Take all upward quantities to be positive.

a.
Consider the vertical component of the motion (uniform acceleration motion):
s(y) = u(y) t + (1/2) a(y) t²
0 = (300 sin45°) t + (1/2) (-9.8) t²
t ≠ 0, and thus t = 43.3 s

Consider the horizontal component of the motion (uniform velocity):
Maximum horizontal range = u(x) t = (300 cos45°) × 43.3 = 9190 m

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b.
Consider the vertical component of the motion:
s(y) = u(y) t + (1/2) a t²
s(y) = (300 sin45°) (1.20) + (1/2) (-9.8) (1.20)² = 248 m

Consider the horizontal component of the motion:
s(x) = u(x) t = (300 cos45°) (1.20) = 255 m

Distance between the final and initial positions = √(248² + 255²) = 356 m
Angle made between the final and initial positions = tan⁻¹(248/255) = 44.2°

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c.
Consider the vertical component of the motion:
v(y) = u(y) + a(y) t
v(y) = (300 sin45°) + (-9.8) (2.00) = 193 m/s

Magnitude of velocity = √[193² + (300 cos45°)°] = 287 m/s
At an angle made with horizontal = tan⁻¹[193/(300 cos45°)] = 42.3°

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d.
Consider the vertical component of the motion:
v(y)² = u(y)² + 2 a(y) s(y)
0 = (300 sin45°)² + 2 (-9.8) s
Height it will going up, s(y) = 2300 m

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e)
Consider the vertical component of the motion:
s(y) = u(y) t + (1/2) a(y) t
0 = (300 sin45°)t + (1/2) (-9.81) t²
t ≠ 0, and thus time taken when it stays in the air, t = 43.2 s
2020-07-27 1:08 pm
Θ o = 45°, therefore :
Vox = Vo*cos 45° = 300*√ 2 / 2 = 150√ 2 m/sec (≅ 212)
Voy  = Vo*sin 45° = 300*√ 2 / 2 = 150√ 2 m/sec (≅ 212)

a. What is its maximum horizontal range R ?
R = Vo^2/(1000*g)*sin (2Θ o) = 300^2/9,807*1 = 9.18 km

b. Where is the ball after 1.20s?
Y = Voy*1.2-g/2*1.2^2 = 180√ 2-4.9035*1.44 = 247 m
X = Vox*1.2 = 180√ 2 m (≅ 255)

c. What is its velocity V after 2.00s?
Vy = Voy-g*t = 150√ 2-9,807*2 = 193 m/sec
Vx = Vox = 212 m/sec
V = √ 212^2+ 193^2 =  286 m/sec 

d. At what height hmax will it go upward?
hmax = Voy^2/2g = 150^2*2/19.614 = 2295 m (just R/4) 

e. How long t will it stay in the air?
t =2*tup = 2*Voy/g = 30.6√ 2 sec (≅ 43.3)


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