Physics behind
Teachers use mousetrap cars to help students better understanding on some primary concepts of physic through hands-on experience learning.
Forces;
One of the foundation concepts of physics, a force may be thought of as any influence which tends to change the motion of an object. In mechanics, forces are seen as the causes of linear motion, whereas the causes of rotational motion are called torques. The action of forces in causing motion is described by Newton's Laws under ordinary conditions, although there are notable exceptions.
Source; http://hyperphysics.phy-astr.gsu.edu/hbase/force.html#defor
Newton's First Law states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force. It may be seen as a statement about inertia, that objects will remain in their state of motion unless a force acts to change the motion.
Newton's second law of motion can be formally stated as follows: The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object.
Newton's third law: All forces in the universe occur in equal but oppositely directed pairs. There are no isolated forces; for every external force that acts on an object there is a force of equal magnitude but opposite direction which acts back on the object which exerted that external force.
Many forces are applied for our mouse trap car to move forward. Understanding those forces will help you achieve a better performing car.
A rigid lever can approach an ideal machine since there is very little loss. From torque equilibrium we see that a resistance force Fr can be balanced by a smaller effort force Fe = (Lr/Le)Fr. This is often stated in terms of the ideal mechanical advantage Fr/Fe = Le/Lr shown in the illustration.
Since we know by conservation of energy that no machine can output more energy than was put into it, the ideal case is represented by a machine in which the output energy is equal to the input energy. For simple geometries in which the forces are in the direction of the motion, we can characterize the ideal machine in terms of the work done as follows: Ideal Machine: Energy input = Energy output
Work input = Fedinput = Frdoutput = Work output
From this perspective it becomes evident that a simple machine may multiply force. That is, a small input force can accomplish a task requiring a large output force. But the constraint is that the small input force must be exerted through a larger distance so that the work input is equal to the work output. You are trading a small force acting through a large distance for a large force acting through a small distance. This is the nature of all the simple machines above as they are shown.
Of course, it is also possible to trade a large input force through a small distance for a small output force acting through a large distance. This is also useful if what you want to achieve is a higher velocity. Many machines operate in this way.
Source;http://hyperphysics.phy-astr.gsu.edu/hbase/mechanics/lever.html
A torque is an influence which tends to change the rotational motion of an object. One way to quantify a torque is
Torque = Force applied x lever arm
The lever arm is defined as the perpendicular distance from the axis of rotation to the line of action of the force. For example, if a person places a force of 10 N at the terminal end of a wrench that is 0.5 m long (or a force of 10 N exactly 0.5 m from the twist point of a wrench of any length), the torque will be 5 N.m
Source;http://hyperphysics.phy-astr.gsu.edu/hbase/torq.html#torq
Tension
In physics, although tension is not a force, it does have the units of force and can be measured in newtons (or sometimes pounds-force). The ends of a string or other object under tension will exert forces on the objects to which the string or rod is connected, in the direction of the string at the point of attachment. These forces due to tension are often called "tension forces." There are two basic possibilities for systems of objects held by strings:[1] either acceleration is zero and the system is therefore in equilibrium, or there is acceleration and therefore a net force is present in the system.
Source;https://en.wikipedia.org/wiki/Tension_(physics)
Frictional resistance to the relative motion of two solid objects is usually proportional to the force which presses the surfaces together as well as the roughness of the surfaces. While this general description of friction (which I will refer to as the standard model) has practical utility, it is by no means a precise description of friction. Friction is in fact a very complex phenomenon which cannot be represented by a simple model. Almost every simple statement you make about friction can be countered with specific examples to the contrary. Saying that rougher surfaces experience more friction sounds safe enough - two pieces of coarse sandpaper will obviously be harder to move relative to each other than two pieces of fine sandpaper. But if two pieces of flat metal are made progressively smoother, you will reach a point where the resistance to relative movement increases. If you make them very flat and smooth, and remove all surface contaminants in a vacuum, the smooth flat surfaces will actually adhere to each other, making what is called a "cold weld".
Source;http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html
Kinetic Energy
Kinetic energy is energy of motion. The kinetic energy of an object is the energy that it possesses due to its motion.[1] It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. The same amount of work is done by the body in decelerating from its current speed to a state of rest.
Source; https://en.wikipedia.org/wiki/Kinetic_energy
Potential Energy
Potential energy is the energy that an object has due to its position in a force field or that a system has due to the configuration of its parts. As for example, the elastic potential energy of an extended spring. Elastic energy is the potential mechanical energy stored in the configuration of a material or physical system as work is performed to distort its volume or shape. Elastic energy occurs when objects are compressed and stretched, or generally deformed in any manner.
Source; https://en.wikipedia.org/wiki/Elastic_energy
Momentum
Linear momentum or translational momentum is the product of the mass and velocity of an object. For example, a heavy truck moving rapidly has a large momentum—it takes a large or prolonged force to get the truck up to this speed, and it takes a large or prolonged force to bring it to a stop afterwards. If the truck were lighter, or moving more slowly, then it would have less momentum.
Source; https://en.wikipedia.org/wiki/Momentum