Momentum (p) equals mass (m) times velocity (v). p=mv * The symbol for “p” came from the word progress which is defined as “the quantity of motion with which proceeds in a certain direction.” It is a vector quantity and the direction is the same as the velocity.

An object can continue to gain momentum as it speeds up. The amount of momentum an object has depends on its velocity and mass. An object with a large mass and slow velocity will still have a larger momentum than an object with a small mass and same velocity. For example, a bowling ball will have more momentum than a playground ball at the same velocities. Hailstones are an example of an object with a small mass with a very high velocity. This results in a big momentum and the ability to cause lots of damage.

A 2250 kg pickup truck has a velocity of 25 m/s to the east. What is the momentum of the truck? Given: m=2250 kg v=25m/s to the east Unknown: p=? Equation: p= mv

p=(2250kg)(25m/s) p = 5.6 X 10 4 kg m/s to the east HINT: Your calculator may give you the answer of Since the value of velocity is only two significant figures, it must be shown in scientific notation.

The larger the momentum of an object, the larger the force has to be to stop the object. For example, “imagine a toy truck and a real dump truck starting from rest and rolling down the same hill at the same time. They would accelerate at the same rate, so their velocity at any instant would be the same, but it would take much more force to stop the massive dump truck than to stop the toy truck in the same time interval.

force X time interval = change in momentum This equation means that if an external force is applied to the object for a certain amount of time, than the momentum will change. The larger the force, the smaller the time interval needs to be to slow the object, or reduce its momentum.

F ∆ t = ∆p F∆t – this is known as the impulse of the force for the time interval. Impulse for a constant external force, is the product of the force and the time over which it acts on an object. So, as the time interval is increased, the amount of force needed to change the momentum decreases.

Highway engineers use the equation to find safe following distances and stopping times. In order to determine proper stopping distance, speeds and weights need to be taken into account. Another factor is what is on the road – such as ice or water.

When object “A” collides with object “B”, object “B” will gain momentum from object “A”. However, the amount of momentum after the collision will equal the total amount of momentum before the collision. This is known as the law of conservation of momentum. This law is “the total momentum of all objects interacting with one another remains constant regardless of the nature of the forces between the objects.”

Momentum is conserved in interactions between two or more objects. Even when the objects push off from each other, the momentum obtained from the interaction equals the momentum before the interaction. This can be seen when two skaters stand facing each other and push each other away.

m 1 v 1,i -m 1 v 1,I = -(m 2 v 2,f -m 2 v 2,i ) This formula means that the resulting momentum of an object after a collision is equal and opposite to the momentum of the other object.

Perfectly inelastic collisions occur when an object runs into another object and they continue to move together after the collision. For example, a meteorite colliding with Earth. Equation: m 1 v 1,i +m 2 v 2,i =(m 1 +m 2 )v f The kinetic energy after a perfectly inelastic collision does not equal the kinetic energy before the collision. This is because some of the energy is converted to other forms of energy.

With an elastic collision, the objects remain in their original shape and no kinetic energy is lost. Also, the objects move separately after the collision. Typically, collisions are neither perfectly inelastic or elastic. Rather, they are inelastic. This means that the objects continue to move separately after the collision but they lose kinetic energy.

Momentum – a vector quantity defined as the product of an object’s mass and velocity. Impulse – for a constant external force, the product of the force and the time over which it acts on an object. Perfectly inelastic collision – a collision in which two objects stick together and move with a common velocity after colliding. Elastic collision – a collision in which the total momentum and the total kinetic energy remain constant.