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Unformatted text preview: Lab 4: Projectile Motion SAR Physics Andrew M Kolchin A projectile is an object thrown at an initial velocity which we will call v . In general, v can have both x (horizontal) and y (vertical) components. Here, in this lab, we will only study projectile motion in which v is completely in the horizontal direction. From now on, well call the horizontal speed: v x . Also, well only look at projectile motion close to the surface of the Earth where the acceleration due to gravity is: g = 9 . 8 m/s 2 Well be rolling a ball off a table at different horizontal speeds and: 1. predicting the horizontal distance ( d pred. ) away from the tabletop at which the ball hits the floor, based on measure- ments of the tabletops height ( h ) and the balls horizontal speed ( v x ). ( pred. stands for predicted). 2. measuring this same distance ( d exp. ) away from the table- top using a meterstick and some other materials. ( exp. stands for experimental.) Suppose we just drop the ball from the tabletops height ( h ). The ball will take a certain amount of time to fall to the floor. Lets call this time t tof , which stands for time of flight . Now suppose we do the same thing, but give the ball a bit of a nudge, 1 that is, an initial horizontal speed v x . Now how long will the ball take to fall to the floor? In each case the initial speed in the y-direction is m/s , so each case will have the same time of flight ( t tof ). We can get the time of flight by measuring the height ( h ) of the tabletop: h = 1 2 g t 2 tof You have seen this equation before for distance fallen from rest under the acceleration due to gravity. In this case, the distance fallen is just the height of the tabletop from the floor ( h ). We can solve this equation for the time of flight t tof : t tof = q 2 h/g 2 So, we have the time (...
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