Physics 122D Collisions and Explosions Worksheet
1. A 4.0kg object is travelling south at a velocity of 2.8m/s when it collides with a 6.0kg object
travelling East at a velocity of 3.0m/s. If these two objects stick together upon collision, at what
velocity do the combined masses move immediately after they collide? 2.12m/s@ E 31.9oN
2. A 4.0kg object is moving East at an unknown velocity when it collides with a 6.1kg stationary
object. After the collision, the 4.0kg object us travelling at a velocity of 2.8m/s E32oN and the
6.1kg object us travelling at a velocity of 1.5m/s E41oS. What was the velocity of the 4.0kg object
before the collision? 4.1 m/s East
3. An object explodes into 3 equal masses. One mass moves East at a velocity of 15.0m/s. If a second
mass moves at a velocity of 10.0m/s E45oS, what is the velocity of the third mass? 23.2m/s @
W17.8oN
4. A 750g red ball traveling at 0.30m/s East hits a 550g blue ball traveling at 0.50m/s West. After the
collision, the red ball moves away at 0.15m/s [E30.0oS]. What is the final velocity of the blue ball?
Determine the amount of kinetic energy lost. 0.287m/s @ W20.9oN, Ek lost = 0.0714J
5. A child drops a shape made from three megablocks on the floor. Each of the mega blocks has a
mass of 22.0g. The three pieces break apart, with the first piece having a velocity of 0.450m/s @ E
62.0oN. The second piece has a velocity of 0.335m/s @ W12.0oS. What is the velocity of the third
piece? 0.348m/s @ E70.4oS
6. Determine whether Question #2 is an elastic or inelastic collision. If it is inelastic, how much
energy is lost? Inelastic, 11.1J of energy lost
7. In rural Minnesota, U.S.A., there is a dark matter detector known as the Cryogenic Dark Matter
Search (CDMS) located 700 m underground in an abandoned mine. It involves collisions between
Germanium atoms and WIMPs (theoretical dark matter particles).
According to the weakly interacting massive particle (WIMP) theory of dark matter, billions of WIMPs
from outer space are raining down on Earth each second. Although they typically pass through solid
objects as if they are not there, there is a very small chance that a WIMP will collide with a nucleus of an
atom within any material it happens to pass through. As a result, at CDMS there is a very small
probability that a WIMP will collide with the nucleus of a germanium atom within the detector, as
illustrated below:
In the figure above, a WIMP with a mass of 1.07 x 10–25 kg and an initial speed of 230 km/s collides
with a stationarygermanium nucleus with a mass of 1.19 x 10–25 kg. If the WIMP is deflected and its
speed is reduced to 75 km/s, use conservation of energy to determine how much energy is transferred
to the nucleus. (It is this energy that scientists must somehow detect.) In calculating your answer,
assume that the collision is elastic.
