Lab help Ballistic pendulum

In summary, the conversation discusses an experiment where a steel marble is shot out of a launcher and collides with a "catcher" on a ballistic pendulum. The pendulum then swings up and reaches a maximum height, providing the height for the gravitational potential energy. The mass of the marble is given, and the goal is to find the initial velocity of the marble. The formula (.5)(m)(v^2)=mgh is used to find the starting velocity, but the perfectly inelastic collision formula is also needed. However, since the mass of the "catcher" is unknown, the calculation cannot be completed. The conversation ends with the realization that the mass of the "catcher" is necessary to find the initial velocity
  • #1
ussjt
41
0
A steel marble is shot out of a launcher (straight) in a "catcher" on a ballistic pendulum. The pendulum then swings up into its max height ans stops. At that point...the height for the gPE is .163 m. The mass of the marble is .0558g. I need to find the inital velocity of the marble. I solve (.5)(m)(v^2)=mgh to find the starting velocity for that, which is the final velocity after the perfctly inelasic collusion. But what happens is that I use the perfctly inelasic collusion formula, m1v1 + m2v2 = (m1 +m2)v' , but I always end up with two variable because I don't know m2. This is where I get stuck. I know the velocity should be some where around 3.5, but I'm not getting close. Please help me..I attached a diagram, I hope it works.
 
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  • #2
Sorry for the double post...but could someone one help me ASAP. Thanks.
 
  • #3
Can't find the diagram, but:
What do you get if you assume the mass of the pendulum to be much less (negligible) to the mass of the steel ball?
 
  • #4
ussjt said:
I solve (.5)(m)(v^2)=mgh to find the starting velocity for that, which is the final velocity after the perfctly inelasic collusion.
Right, assuming you really mean: (.5)(m1 + m2)(v'^2)=mgh.
But what happens is that I use the perfctly inelasic collusion formula, m1v1 + m2v2 = (m1 +m2)v' , but I always end up with two variable because I don't know m2. This is where I get stuck.
Since the speed of the "catcher" is zero before the collision, you mean:
m1v1 = (m1 +m2)v', where v1 is the speed of the marble.

There's no way around it: You need the mass of the "catcher" if you wish to find v1.
 

1. What is a ballistic pendulum?

A ballistic pendulum is a scientific instrument used to measure the velocity of a projectile. It consists of a pendulum suspended from a fixed point and a target at the bottom of the pendulum's swing. When a projectile hits the target, it causes the pendulum to swing and the height of the swing can be used to calculate the projectile's initial velocity.

2. How is the velocity of a projectile calculated using a ballistic pendulum?

The velocity of a projectile can be calculated using the equation: v = m * sqrt(2gh), where v is the velocity, m is the mass of the projectile, g is the acceleration due to gravity, and h is the height of the pendulum swing. This equation assumes conservation of energy and momentum.

3. What factors can affect the accuracy of a ballistic pendulum measurement?

Several factors can affect the accuracy of a ballistic pendulum measurement, including air resistance, friction in the pendulum's pivot point, and the elasticity of the target material. Other sources of error may include human error in measuring the height of the pendulum swing and variations in the projectile's mass or velocity.

4. How can the accuracy of a ballistic pendulum measurement be improved?

To improve the accuracy of a ballistic pendulum measurement, it is recommended to use a larger and heavier target, reduce air resistance by using a vacuum chamber, and minimize friction in the pendulum's pivot point. Additionally, taking multiple measurements and calculating the average can also help to improve accuracy.

5. What are some real-world applications of the ballistic pendulum?

The ballistic pendulum has many practical applications, such as in forensic science to analyze bullet trajectory and velocity, in ballistics testing to measure the performance of firearms, and in physics experiments to demonstrate the principles of conservation of energy and momentum. It is also used in sports such as archery and golf to measure the initial velocity of a projectile.

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