Prelab for the Ballistic Pendulum

Transcription

1 Ballistic Pendulum 1 Prelab for the Ballistic Pendulum 1. Write the general horizontal and vertical motion Kinematics equations for a horizontally launched projectile. 2. Write the relevant Conservation of Momentum equation for a case where a moving object with mass m 1 collides and sticks to a stationary object with mass m Write the Conservation of Energy equation for an object with mass m that moves up an incline and stops at height h (assume no friction). 4. The measured length of the pendulum from its pivot point to the center of mass is 20 cm. If the cup pivots 60 o after the ball is shot into it, then determine the height of the center of mass.

2 Ballistic Pendulum 2 5. When a 0.10 kg ball is launched with an initial velocity into a stationary cup with mass 0.15 kg, the ball and cup rise 10 cm. Determine the initial velocity of the ball and cup. 6. A 0.10 kg ball is launched with an initial velocity into a stationary cup with mass 0.15 kg. After the perfectly inelastic collision, the two objects travel with a velocity of 1.4 m/s. Determine the initial velocity of the ball. 7. A ball travels horizontally off a table 1.0 meters high with a velocity of 18 m/s. If the ball is to travel through the center of a hoop which is placed 0.20 meters above the ground, then how far from the base of the table should the center of the hoop be placed?

3 Ballistic Pendulum 3 Ballistic Pendulum and Projectile Motion INTRODUCTION 1. Investigate Conservation of Momentum in an elastic collision between a ball and a ballistic pendulum. 2. Investigate the kinetic energy loss in the collision of the ball with the pendulum. 3. Determine the initial velocity of the ball by the gun. 4. Determine the projectile range of the ball with an initial velocity launched from a specific height. MATERIALS Figure 1. Materials used in the "Ballistic Pendulum" lab. Ballistic pendulum apparatus with projectile ball Laboratory balance Meter stick II. THEORY In your lab report, define conservation of momentum and conservation of energy. List the five major equations (not including conservation of momentum and conservation of energy equations) for this lab. III. EXPERIMENTAL 1. Slide the projectile ball into the barrel of the spring gun (Figure 2. Make sure you push the ball into the Short Range notch. (During later trials, your group will use the Medium Range and Long Range notches).

4 Ballistic Pendulum 4 Figure 2. Projectile Launcher. Note the yellow line that appear above the Medium Range window. This indicates that the ball is set to launch at the Medium Range. 2. Make sure the pendulum cup is stationary and not oscillating. Lower the angle-measuring indicator to 0 degree. [Note: the ball has a tendency of rolling away from the launcher, so make sure the ball is pushed into the launcher before you fire it.] 3. Hold the apparatus steady with one hand, and with the other, pull up on the string. This fires the ball into the pendulum cup, which will force the cup to move upward in an arc motion. 4. Record the result in the Table Take five trial at each range. IV. RESULT 1. Measure mass of the ball (m ball ) 2. Measure mass of the pendulum cup and rod (m cup ) 3. Measure the mass of the cup when the ball is placed inside the cup (m ball +m cup ) 4. Measure the distance from the pivot point of the pendulum to the center of mass of the cup and the ball in it. [The center of mass of the pendulum is the spot where the entire pendulum can be balanced at one point.] L = 5. Angle positions:

5 Ballistic Pendulum 5 Table 1: The angle that the pendulum rises as the balls are shot from different notches. Notch θ 1 θ 2 θ 3 θ 4 θ 5 θ ave Short Medium Long Table 2: Determining the speed of the ball from the analysis of the data in Table 1. Notch h V cup + ball v ball Short Medium Long Analysis: h was the height that the pendulum rose after the ball was launched into it. Determine the value of h using the appropriate values and trigonometry (Note: if you are having problems, draw the sketch, include L and θ ave in the sketch). Calculations of v cup + ball and v ball are similar to the calculation you did on last week s homework. Extra Credit: This part is done in groups of two or individually. You and your group will be disqualified if you receive help from someone who is not in your group of two. [Show calculations on how you determined the location of the target: note the Homework you did last week should aid you in your calculations]. If your group gets the ball into the target on the within two trials, each member in your group will receive credit.