PHYS 031 Chapter Notes - Chapter 4: Projectile Motion, Shot Put

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yellowbutterfly42

4 Mar 2013

School

University of Vermont

Department

Physics

Course

PHYS 031

Professor

Jie Yang

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Document Summary

Projectile motion is motion with constant acceleration in the x and y direction. X-direction is horizontal, while y-direction is vertical. X direction: 0 m/s y direction: -9. 8 m/s . Work in each direction separately initial conditions for x-direction initial conditions for y-direction. A boy throws a shot-put with an initial velocity of 12 m/s 40 degrees above the horizontal 1. 80 meters above the ground. Vy = v sin(40: from initial position to maximum height (y-max) At y-max 0 = vy - gt y-max = h + vy - gt : from y-max to ground. Vy = 0 m/s when t = t . A football is thrown with an initial speed of 30 m/s 60 degrees above the horizontal, and hits the ground 7. 5 seconds later. Vy = vy - gt (at y-max) y-max = h + vy t - gt .

Related Questions

A projectile of mass 0.38 kg is shot from a cannon, at height 6.8m, as shown in the figure, with an initial velocity vi, having ahorizontal component of 4.6 m/s.
The projectile rises to a max height of (delta y) above the end ofthe cannon's barrel and strikes the ground a horizontal distance(delta x) past the end of the cannon's barrel.

Find the magnitude of the velocity vector when the projectile hitsthe ground. The acceleration of gravity is 9.8 m/s2. Answer inunits of m/s.

A student stands at the edge of a cliff and throws a stonehorizontally over the edge with a speed of vi = 18.2 m/s. The cliffis h = 49.5 m above a body of water as shown in the figurebelow.

(a) What are the coordinates of the initial position of the stone?(Do not assume that the student is the point of origin.)

(b) What are the components of the initial velocity of thestone?

(c) What is the appropriate analysis model for the vertical motionof the stone? (Select all that apply.)
5

constant velocity motion free fall motion g = 9.8 m/s2 noacceleration from gravity g = -9.8 m/s2

(d) What is the appropriate analysis model for the horizontalmotion of the stone? (Select all that apply.)
6

constant velocity in the horizontal direction g = 9.8 m/s2 g = -9.8m/s2 free fall motion no acceleration from gravity

(e) Write symbolic equations for the x and y components of thevelocity of the stone as a function of time. (Use the following asnecessary: vix, g, and t.)

(f) Write symbolic equations for the position of the stone as afunction of time. (Use the following as necessary: vix, g andt.)

(g) How long after being released does the stone strike the waterbelow the cliff?

(h) With what speed and angle of impact does the stone land?

In the latest Indian Jones film, Indy is supposed to throw agrenade from his car, which is going 82.0 km/h, to his enemy's car,which is going 125km/h. The enemy's car is 14.6m in front of theIndy's when he lets go of the grenade.

=====>Part A: What is the Vo ? in km/h

If Indy throws the grenade so its initial velocity relative to himis at an angle of 45 ^\circ above the horizontal, what should themagnitude of the initial velocity be? The cars are both travelingin the same direction on a level road. You can ignore airresistance.

Hint: The grenade moves in projectile motion, and convert the twovelocities given in the problem from km/hr to m/s. Being anexcellent student of P2, Indy knows that horizontal range of thegrenade must equal the distance that the enemies car is ahead atthe time the grenade is thrown plus the distance the enemies cartravels while the grenade is in the air. This distance is given byv_rel*t, where v_rel the relative velocity of the enemies carrelative to the Indy's and t is the time in the air.

Solve for time that the grenade is in the air in terms ofv_0.

Use the range equation to get the grenade distance as a function ofv_0

Set R=(initial separation)+v_rel*t and get a 2nd order polynomialfor v_0. Use quadratic equation to get v_0. This is the magnitudeof the velocity vector relative to Indy.

=====>Part B: What is Vo in km/h?

Find the magnitude of the velocity relative to the earth.

Hint: Use Galileo's equation where Frame A is ground, Frame B isIndy's car and the object of interest P is the granade.

Use your answer in part A for speed and given direction tocalculate the x and y components of the velocity with respect toIndy's car. The velocity of Indy's car with respect to the groundis straightforward to write in x and y components.

PHYS 031 Chapter Notes - Chapter 4: Projectile Motion, Shot Put

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