Have you ever found yourself walking around an amusement park and found yourself drawn to the bumper cars? I think everyone has. After all, it is a ride that you can have fun on and you can use to take out your frustrations on others. But, have you ever wondered why it is that the other person feels a jolt when you bump their car? That can all be explained by physics and Isaac Newton.
Sir Issac Newton
Newton’s third law of motion says that for every action there is an equal and opposite reaction. Therefore, when one car exerts a force on another, the second car has to exert that same force back.
Here's a quick and fun pop quiz to help you remember
this
law. Now, click on this link and then on “Newton’s Law
Cryptogram.”
Go Play!
Impulse and Momentum:
Momentum is a conserved quantity because it cannot be
created or destroyed. It is represented by the equation p=mv,
which
states that momentum is equal to the mass of an object multiplied by
its
velocity. When there are two cars in a collision, like bumper
cars,
their momentums can be set equal to one another so that
m1v1=m2v2.
From this we see that a car with the smallest mass experiences the
greatest
change in velocity. On the bumper cars, there is just one way to
transfer momentum. This is through an impulse, which is defined
as
force multiplied by time (Impulse=F*t). However, this impulse
must
still obey Newton’s third law. This means that if car one gives
an
impulse to car two, car two must give that same impulse back. So,
even if a heavy man hits a small child while riding the bumper cars,
both
of their cars exerted equal forces on each other over the same amount
of
time.
Yea Collisions!
When two cars hit each other, there are a number of
different
factors involved in the collision. These include the velocity of
the two cars, the masses of the drivers, and the masses of the
cars.
However, since we are concentrating on bumper cars, the masses of the
cars
are negligible because all of the cars are, essentially, the same
mass.
However, when it comes to explaining the other two factors, Newton is,
once again, the man we turn to. According to his law of
acceleration
(F=ma), the greater the mass of an object, the more difficult it is to
change its speed. Therefore, the heavier the person in the car
is,
the less they will travel. Also, the higher velocity that a
person
is moving at, the more they will displace the car that they collide
with.
Have you kept up so far? If so, you can test
your knowledge with an interactive game.
Fun
with Collisions
Obviously, in amusement parks there have to be some safety standards. First of all, each bumper car has a rubber lining all around it so the rider does not feel as strong of a force from the collision. Secondly, each driver must wear a seatbelt. The reason for that also is explained by physics and Newton. Even after a collision, a driver is going to keep moving in the direction the car was moving in originally. This is due to Newton’s first law, or the law of inertia. This states that an object will continue to move on a certain pathway or stay at rest unless acted upon by an external force. So, to prevent people from falling out of their cars, they must wear a restraint device.
A moving bumper car also has kinetic energy, which is directly related to mass and velocity. Kinetic energy is represented by the equation KE=.5mv^2. The higher the velocity the car is moving at and the higher the mass of the car or the driver, the higher the kinetic energy will be.
Example:
A 100kg man is traveling at 4m/s in his 300kg bumper
car. A small child of 50kg is traveling 7m/s in his 300kg bumper
car. Which person has more kinetic energy?
KE=.5mv^2
KEman=(.5)(400)(4)^2
KEman=3200 kg m/s
KEboy=(.5)(350)(7)^2
KEboy=8575kg m/s
Therefore, the velocity of a person has a much larger
impact on their kinetic energy than their mass.
Here's a quick summary of the equations involved
with
the collisions:
| Momentum | p=mv |
| Impulse | Impulse=Ft |
| Law of Acceleration | F=ma |
| Kinetic Energy | KE=.5mv^2 |
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