physics

posted by .

A 0.145 kg block is released from rest from
the top of a 51.7◦ frictionless incline. When
it has fallen a vertical distance of 1.3 m, a
0.00794 kg bullet is fired into the block along
a path parallel to the slope of the incline, and
momentarily brings the block to rest, stopping
in the block.
The acceleration of gravity is 9.8 m/s2 .

a) Find the speed of the bullet just before
impact.

Answer in units of m/s.

b) What bullet speed is needed to send the block
up the incline to its initial position?

Answer in units of m/s.

  • physics -

    First calculate the speed V of the sliding block before it is hit by the bullet. You can use conservation of energy for that, since the incline is frictionless.

    (1/2) M V^2 = M g * 1.3 m
    V = sqrt(2*9.8*1.3) = 5.05 m/s

    The bullet must have an equal and opposite momentum before impact, since the momentum right after impact is zero.
    m v = M V
    where m is the bullet mass and v is the bullet velocity.

    Solve for v.

    AFTER impact, gravity will cause the bullet and block to resume falling together, but you are only worried about the instant after impact, before gravity provides an impulse to increase the momentum again.

  • physics (part b) -

    I did not notice your part b. That is a harder question.

    Use energy conservation to predict the velocity V' (after impact) needed to bring the block and bullet together back to the top of the incline.

    (1/2)(M+m)V'^2 = (M+m)g*1.4
    V' = 5.05 m/s (same as V in part a, but in the opposite drection)

    Now apply conversation of momentum to the impact event, and require that V' (UP the incline) be the final velocity.

    -M V + m v = (M +m) V
    v = (2M/m +1) V

  • physics -

    for part a:

    v= (mass of block/mass of bullet)(sqrt2gh)

    v = (0.145/0.00794) x (sqrt 2x9.8x1.3)

    v = 18.262 x 5.0478

    v= do the calculation

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. physics

    A bullet of mass m= 0.0290 kg is fired along an incline and imbeds itself quickly into a block of wood of mass M= 1.55 kg. The block and bullet then slide up the incline, assumed frictionless, and rise a height H= 1.65 m before stopping. …
  2. physics

    A physics student pulls a block of mass m = 23 kg up an incline at a slow constant velocity for a distance of d = 4 m. The incline makes an angle q = 25° with the horizontal. The coefficient of kinetic friction between the block and …
  3. Physics HELP!

    A 20.0 g bullet is fired horizontally into a 85 g wooden block that is initially at rest on a frictionless horizontal surface and connected to a spring having spring constant 156 N/m. The bullet becomes embedded in the block. The bullet …
  4. Physics- Elena please help!

    A 20.0 g bullet is fired horizontally into a 85 g wooden block that is initially at rest on a frictionless horizontal surface and connected to a spring having spring constant 156 N/m. The bullet becomes embedded in the block. The bullet …
  5. physics

    A small block is released from rest at the top of a frictionless incline. The distance from the top of the incline to the bottom, measured along the incline, is 3.60 m. The vertical distance from the top of the incline to the bottom …
  6. Physics

    An 8.00g bullet is fired at 220m/s into a 250g wooden block that is initially at rest. The bullet remains in the block and after the collision the two slide up a 30° incline. a. Solve for the velocity of the bullet-block after the …
  7. Physics

    An 8.00g bullet is fired at 220m/s into a 250g wooden block that is initially at rest. The bullet remains in the block and after the collision the two slide up a 30 degree incline. a) Solve for the velocity of the bullet block after …
  8. physics

    A small block is released from rest at the top of a frictionless incline. The distance from the top of the incline to the bottom, measured along the incline, is 3.70 m. The vertical distance from the top of the incline to the bottom …
  9. physics

    A small block with mass 0.200 kg is released from rest at the top of a frictionless incline. The block travels a distance 0.440 m down the incline in 2.00 s. The 0.200 kg block is replaced by a 0.400 kg block. If the 0.400 kg block …
  10. physics

    A frictionless incline is 5.00 m long (the distance from the top of the incline to the bottom, measured along the incline). The vertical distance from the top of the incline to the bottom is 4.03 m. A small block is released from rest …

More Similar Questions