-3. At the top of a clit 70 m high, Raoul throws a rock upward with velocity 33

Question

-3. At the top of a clit 70 m high, Raoul throws a rock upward with velocity 33 m/s How much latcr should hedrsecond rock from rest o botdh rocks aiv D) 1.316 sec E) 1.974 sec do 40 ·I- (-9Y1 simultaneously at the bottom of the cliffm A) 12.3 sec B) 6.93 sec C) 4.65 soc -10 : 4. If the velocity of an object is given by V-614-5t 8, when x0-7, what is its displacement after 4.5 seconds A) 618 m B) 564 m C) 108 m D) 2207 m E) 576 m 5. A ball is thrown up in the air with an initial velocity of 34.3 m/s upward. How long does it take the ball to return to the ground? A) 7 s B) 1.9s C) 12.3s D) 2s E) 1.98 s mph m a direction 35° north ofwest what is the new velocity 6. A jet airliner moving at 400 mph due cast moves into a region where the wind is blowing at 300 aircraft? A) 420 mph B) 628 mph C) 980 mph D) 231 mph E) 98 mph . A ball is shot with a velocity of 41 m/'s at an angle of 45e from the top of a 39 m tall building, What is the horizontal distance the ball travels when it hits the A) 47.3N B) 185 m C) 204 m D) 719.6 m E) 138 m

Explanation / Answer

3)Let he drops t time later,

time taken by second rock = sqrt(2h/g) = sqrt(2*70/9.8)

= 3.78 s

Writing second equation of motion for first rock,

h = uT+ 0.5g*T^2

70 = - 33(t+3.78) + 4.9*(t+3.78)^2

Solving for t, t =4.65 s

Option C is correct.

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