A rock is thrown straight up into the air with an initial speed of 85 m/s at time  t = 0.  Ignore air resistance in this problem. At what times does it move with a speed of 13 m/s? Note: There are two answers to this problem.

A stone is thrown at an angle of 30 ° above the horizontal from the top edge of a cliff with an initial speed of 12 m/s. A stop watch measures the stone's trajectory time from top of cliff to bottom to be 4.8 s. What is the height of the cliff? ( g = 9.8 m/s 2 and air resistance is negligible)

A hot air balloon has just lifted off and is rising at a constant rate of 2.0 m/s. Suddenly one of the passengers realizes she has left her camera on the ground. A friend picks it up and tosses it straight upward with an initial speed of 12 m/s. If the passenger is 2.5 m above her friend when the camera is tossed, how high is she above her friend when the camera reaches he ?

An attacker at the base of a castle wall 3.80 m high throws a rock straight up with speed 8.40 m/s from a height of 1.40 m above the ground. (a) Will the rock reach the top of the wall? Yes, No     (b) If so, what is its speed at the top? If not, what initial speed must it have to reach the top? m/s(c) Find the change in speed of a rock thrown straight down from the top of the wall at an initial speed of 8.40 m/s and moving between the same two points. m/s(d) Does the change in speed of the downward-moving rock agree with the magnitude of the speed change of the rock moving upward between the same elevations? Yes, No     (e) Explain physically why it does or does not agree.

An object is thrown upwards from the ground level at a speed of 58m/s. It travels upwards to the highest point of its path and then falls back to the ground. What is the objects speed and direction right as it is about to hit the ground at the end of it's fall? *   24 m/s upwards 24 m/s downwards 0 m/s upwards 9.8 m/s upwards 9.8 m/s downwards 58 m/s upwards 58 m/s downwards

A rocket is launched from a height of 3 m with an initial velocity of 15 m/s. At what time will the rocket be 13 m from the ground?

An attacker at the base of a castle wall 3.60 m high throws a rock straight up with speed 7.50 m/s from a height of 1.60 m above the ground. a) what is its speed at the top? If not, what initial speed must it have to reach the top? b) Find the change in speed of a rock thrown straight down from the top of the wall at an initial speed of 7.50 m/s and moving between the same two points. c) Does the change in speed of the downward-moving rock agree with the magnitude of the speed change of the rock moving upward between the same elevations? d) Explain physically why it does or does not agree.

An object is launched horizontally at a height of 30 m with an initial velocity of 20 m/s. The x-component of the initial velocity is:    answer choices 20 m/s 0 m/s 15 m/s not enough information

A swimmer bounces straight up from a diving board and falls feet first into a pool. She starts with a velocity of 4.0 m/s, and her takeoff point is 1.1 m above the pool.  Which of these two valid methods is the easiest to find how long her feet are in the air? Group of answer choices Break the problem in two parts. For part 1, find the time to reach her highest point by using v0 = 4 m/s, a = -9.8 m/s2, and vf = 0 m/s.  For part 2, you can use the highest point above the board found in the previous problem and add it to her height above the pool. Then, using v0 = 0 m/s and a = -9.8 m/s2, you can find the time to reach the ground. Since you only care about the end points in this case, you can use v0 = 4 m/s, a = -9.8 m/s2, and Δy = -1.1 m to find the time to reach the ground.

A student launches a small rocket which starts from rest at ground level. At a height h=1.04km, the rocket reaches a speed of vf=391m/s. At that height, the rocket runs out of fuel, so there is no longer any thrust propelling it. After the rocket's engine turns off at a height of h=1.04km, it continues to move upward due to the velocity that it reached. What is the rocket's acceleration, in meters per squared second, during the period from engine shutoff until it returns to the ground? Ignore air resistance.