A rock, released at rest from the top of a tower, hits the ground after 1.5 s. W

Question

A rock, released at rest from the top of a tower, hits the ground after 1.5 s. What is the speed of the rock as it hits the ground? (g = 9.8 m/s^2 and air resistance is negligible) a. 15 m/s b. 20 m/s c. 31 m/s d. 39 m/s 5. A rifle is aimed horizontally toward the center of a target 100 m away. If the bullet strikes 10 cm below the center, what was the velocity of the bullet? (Ignore air friction.) a. 300 m/s b. 333 m/s c. 500 m/s 6 d. 700 m/s 6. A 70 kg bowling ball experiences a net force of 5.0 N. What will be its acceleration? a. 35 m/s^2 b. 7.0 m/s^2 c. 5.0 m/s^2 d. 0.71 m/s^2

Explanation / Answer

v = u +a*t

Here initial speed, u = 0

So

v = a*t

v = 9.8*1.5

   = 14.7 m/s = 15 m/s (option A)

Q-5

y = v0t + 0.5*g*t^2

Here initial velocity, v0 = 0

So , y = 0.5*g*t^2

0.1 m = 0.5*9.8*t^2

t = 0.143 s

Horizontal Velocity of the bullet,

v0x = x/t

     = 100 / 0.143

    = 700 m/s (option d)

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