check this you will get point. help me which formula . read text below.?

Question

A 28-g rifle bullet traveling 230m/s buries itself in a 3,6 kg pendulum haning on a 2,8m long string, which makes the pendulum swing upward in an arc. Determine te vertical and horizontal components of the pendulum's displacement.

plzzzzzzzzzzzzz tell me in an easy way and which formula do have i to use. plzzz

Answer 1

3 answers and NO help whatsoever! You have to use MOMENTUM first to get the velocity. Energy is almost ALWAYS lost in collisions.

m1v1 = m2v2→ v2 = m1v1/(m1+m2) = .028*230/(.028+3.6)
v2 = 1.775 m/s

After the collision, energy IS conserved as the pendulum swings:
(m1+m2)gYp = .5(m1+m2)(v2)²→ Yp = .5*1.775²/g = .1607 m

Since R(1-cosθ) = Yp, cosθ = 1-Yp/R = .9246→ θ = 19.5° so,
Xp = 2.8sin19.5 = .935 m

Answer 2

The only way I can think of answering this problem is if you assume that all the energy from the bullet transfers to the pendulum w/o any energy loss. If that is the case, you can figure out the kinetic energy of the bullet. (1/2*mass of bullet*velocity of bullet^2) (mass in kg not g) This energy all transfers into the new bullet and pendulum system, which swings up some displacement and stops moving, meaning all the energy is now potential. You take the nymber you found for the bullets KE and figure out the height the pendulum travelled by making the Ke equal to the new systems PE (mass of bullet and pendulum*gravity*height). When you get the height, you can make a triangle because you have the vertical displacement, the angle from the horizontal can be found by using some inverse sine algebra. the hypotenuse would be length L of the pendulum. the opposite side from the angle will be (L minus H *found in the mgh) then using sin^-1 of (L-H/L) you will have the max angle the pendulum makes with the horizontal. 90 minus this angle would give you the angle between starting position and beginning position

Answer 3

It’s not so much which “formula” to use as it is understanding the problem. Physics is not about plugging values into formulas to get answers.

In your problem the bullet is presumably traveling horizontally and has kinetic energy equal to half its mass times the square of its velocity, both of which are given. The bullet hits and is retained by a massive pendulum, which swings upward to some height, h, until the kinetic energy of the pendulum equals the potential energy due to gravity at height h.

To assume this potential energy is equal to the original kinetic energy of the bullet is naive. Some energy was lost in penetrating the pendulum and is converted to heat.

Knowing the mass of the pendulum and the length of the string supporting it are the only other information you provided. This is not enough to calculate h, from which the horizontal displacement could also be calculated using the length of the string.

You need to know what fraction of the bullet kinetic energy was transferred to kinetic energy of the pendulum. Not knowing the height, h, the only way to know how much energy was transferred is to know how fast the pendulum recoiled. Since you didn’t specify that either, the problem cannot be solved with the information given.

In this experiment, the height, h, is usually the independent variable that is measured to calculate the bullet velocity.

Answer 4

Consider what's happening - you've got a bullet with kinetic energy (.5 mv^2). All that kinetic energy's going to be transferred to the pendulum when the bullet hits it (but don't forget that the bullet's now part of the pendulum - you need to include its mass) and the pendulum will swing up until all the kinetic energy's been converted to potential energy (mgh), at which point it stops i.e. potential energy = kinetic energy. You've got the formulae for those so now you can work out the vertical component (h).

There are a number of ways of calculating the horizontal displacement. I used Pythagoras' theorem, but only because I can't remember any trig!