Bullet in Block- 2D Projectiles w/ Motion

AI Thread Summary
A 9 g bullet is fired into a 396 g block at rest on a frictionless table, leading to a combined motion after impact. The block lands 2.3 m from the table's edge, and the vertical drop time is calculated to be approximately 0.43 seconds. The horizontal initial velocity of the block and bullet combination is determined to be about 5.37 m/s. For the collision analysis, the conservation of momentum equation m1v1i + m2v2i = m1v1f + m2v2f is recommended for solving the bullet's initial velocity. This approach clarifies the roles of the bullet and block in the momentum exchange during the collision.
physicsluv
Messages
14
Reaction score
0

Homework Statement



A(n) 9 g bullet is fired into a 396 g block
that is initially at rest at the edge of a frictionless table of height 0.9 m. The bullet remains
in the block, and after impact the block lands
2.3 m from the bottom of the table.
The acceleration of gravity is 9.8 m/s.

Homework Equations



ΔX = Vi(t) + (1/2)(a)(t^2)

m(Vf-Vi) = -m(Vf-Vi)

The Attempt at a Solution


I separated the equation into vertical and horizontal parts.

Horizontal: ΔX=2.3, a = 0 m/s/s
Vertical: ΔY= .9, a= -9.8 m/s/s, Vi = 0 m/s (because it is launched horizontally).

Using the kinematic equation ΔX = Vi(t) + (1/2)(a)(t^2) to solve for the vertical time:
t = 0.4285714286 seconds

Since the vertical time is equal to the horizontal time, I plugged this time into the same kinematic equation to solve for the horizontal Vi:
Vi = 5.366666667 m/s

Now, I know you need to use the collision equation to solve for the initial velocity in the bullet, but I do not know how to set it up...
I have this so far

9(5.366666667-vi)=-____?_____

Thank you for the help :)
 
Physics news on Phys.org
m(Vf-Vi) = -m(Vf-Vi) That is not the collision equation I am familiar with. With just a single m, it suggests a collision involving a single object, an oxymoron if I've ever heard one. Try m1v1i+m2v2i=m1v1f+m2v2f
You should then be able to quickly simplify one side by equating one velocity with another, and it will all fall out from there.
 
Barakn said:
m(Vf-Vi) = -m(Vf-Vi) That is not the collision equation I am familiar with. With just a single m, it suggests a collision involving a single object, an oxymoron if I've ever heard one. Try m1v1i+m2v2i=m1v1f+m2v2f
You should then be able to quickly simplify one side by equating one velocity with another, and it will all fall out from there.
What would m2, v2i, and v2f be?
 
m2 would be mass of the block, v2i is the initial velocity of the block, and v2f is the final velocity of the block
 
I got it, thanks!
 
Thread 'Collision of a bullet on a rod-string system: query'
In this question, I have a question. I am NOT trying to solve it, but it is just a conceptual question. Consider the point on the rod, which connects the string and the rod. My question: just before and after the collision, is ANGULAR momentum CONSERVED about this point? Lets call the point which connects the string and rod as P. Why am I asking this? : it is clear from the scenario that the point of concern, which connects the string and the rod, moves in a circular path due to the string...
Thread 'A cylinder connected to a hanged mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top