Question

3. A ball is thrown straight up from an initial height of 1.75 m. It hits the ground eight seconds later. What was the initial s eed of the ball? 4. You are at the helm of the USS Sisko about to set out for Arrakis, the maiden voyage of the first exploratory star cruiser commissioned by the UAC. The ship is at dock near Magrathea and is not currently moving, but your captain, Malcom Reynolds, wants to test the auxiliary thrusters. The comet Tyrell is about 100,000 km from where you are and is moving directly away from you at 70 km/s. Capt. Reynolds wants to know if the ship can reach the comet in less than a minute. You know the thrusters can produce about 100 km/s2 of acceleration. Should vou tell him that vou can make it? 5. An object is traveling at 20 m/s, but is accelerating at -5 m/s2. After six seconds the object begins to slow and has come to a stop five seconds later. Draw graphs of position, velocity and acceleration versus time (each on separate axes) for this object. Be quantitative. Specify the position, velocity, acceleration and time for point(s) when the object has stopped

Answer 1

here we use equations of kinematics for the solution, ***************************************************************************************************
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Here we use equations of kinematics for the solution, let us take initial launch point as origin and downward as positive, so, S = V_i t + 1/2 at^2 -(1) Here s = h = 1.75 m t = 8 s a = g = 9.8 m/s^2 Put these values in equation (1) above and we get v_i = -38.98 m/s So, speed = Vertical-bar v_i Vertical-bar = 38.98 m/s