Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dynamics of drag and force distributions for projectile impact in a
  granular medium   Our experiments and molecular dynamics simulations on a projectile
penetrating a two-dimensional granular medium reveal that the mean deceleration
of the projectile is constant and proportional to the impact velocity. Thus,
the time taken for a projectile to decelerate to a stop is independent of its
impact velocity. The simulations show that the probability distribution
function of forces on grains is time-independent during a projectile's
penetration of the medium. At all times the force distribution function
decreases exponentially for large forces.

26
The categories of this paper are: bayes-an
16
The categories of this paper are: stat
0
The categories of this paper are: hep-ph
31
The categories of this paper are: ao-sci
35
The categories of this paper are: mtrl-th
17
The categories of this paper are: q-fin
1
The categories of this paper are: cs
20
The categories of this paper are: acc-phys
13
The categories of this paper are: quant-ph
10
The categories of this paper are: q-bio
21
The categories of this paper are: adap-org
5
The categories of this paper are: gr-qc
18
The categories of this paper are: econ
27
The categories of this paper are: comp-gas
30
The categories of this paper are: q-alg
14
The categories of this paper are: math-ph