Projectiles Problem: Solve Questions & Improve Test Scores

[aquann]

Homework Statement

just got back my test and did really bad on it. how would you do these question?

1) A rock is fired horizontally off of a cliff at 41 m/s. what is the magnitude of its velocity 5.3s later?

2) a golf ball is thrown out of a window at 15 m/s at an angle of 22* above the horizontal. how far does the golf ball travel horizontally if the window is 25m high?

Homework Equations

The Attempt at a Solution

1) i use this formula v2=v1+(a)(t) and got 81.81m/s

2) blank=/

 

[danago]

For 1, you should consider the horizontal and vertical components of the velocity separately. Assuming that there is no air resistance, the horizontal speed will always be 41 m/s. The vertical speed is initially 0 m/s and is increasing at a rate of 9.8 m/s², and will therefore be v₂=9.8*5.3 = 51.94 m/s after 5.3 seconds has passed. The total resultant speed can then easily be calculated.

For 2, draw a diagram if it helps. First calculate the initial vertical and horizontal components of the velocity using the initial speed and angle of projection. You can then use the vertical speed to calculate how long the ball moves before it hits the ground, and then use this time of flight to find how far horizontally it travels (remember, assuming that there is no air resistance, the horizontal velocity does not change).