Momentum and Unbalanced Forces (Page 30A) Geologic Eras of the Earth: What did the Earth look like in the past? Forces: How do forces and Newton’s laws shape the Earth? Energy: What is energy and how does it affect objects and living organisms on Earth?

What was pulling the asteroid to the Earth What was pulling the asteroid to the Earth? Answer: Gravity and momentum

Momentum and Unbalanced Forces (Page 30A) As the asteroid was hurtling towards the Earth, it was building up something else other than force… MOMENTUM: the quantity of motion an object has or “mass in motion.” Units are in kg*(m/s). Question: For an object to have momentum, what must it also have or be doing? Answer: An object can only have momentum when it is in motion.

Momentum and Unbalanced Forces (Page 30A) The value of an object’s momentum is affected by two variables: mass and velocity. Momentum describes how much of an object is moving (mass) and how fast it is moving (velocity). To calculate momentum: P = (mass)(velocity) Question: What kind of relationship does mass and velocity have with momentum? Answer: Momentum is directly proportional to mass and velocity.

Momentum Practice (Page 30B) A jogger weighing 57 kg is moving at 4.75 m/s. What is their momentum? An ice skater collides into another skater while moving at 11 m/s. They weigh 45 kg. What is their momentum before they hit the skater? A skateboarder weighing 47 kg hops onto a 5 kg skateboard and glides away at 5 m/s. What is their momentum?

Momentum and Unbalanced Forces Practice (Page 30B) A jogger weighing 57 kg is moving at 4.75 m/s. What is their momentum? P = m*v P = (57 kg)(4.75 m/s) = 270.75 kg*m/s 2. An ice skater collides into another skater while moving at 11 m/s. They weigh 45 kg. What is their momentum before they hit the skater? P = (45 kg)(11 m/s) = 495 kg*m/s 3. A skateboarder weighing 47 kg hops onto a 5 kg skateboard and glides away at 5 m/s. What is their momentum? P = (52 kg)(5 m/s) = 260 kg*m/s

Momentum and Unbalanced Forces (Page 30A/31A) How can momentum be affected or changed? 1) Collisions: when two objects come into contact and exert a force on each other. Collisions test an object’s elasticity, or how much an object is deformed from its original shape when a force is applied to it. Question: Give an example of an object with high elasticity and one with low elasticity. Answer: Rubber has high elasticity while concrete has low elasticity.

Momentum and Unbalanced Forces (Page 30A+31A) Collisions are classified in 2 ways, but in both types of collisions, momentum is always conserved. However, kinetic energy is not always conserved. Elastic collisions are collisions where kinetic energy is conserved. Inelastic collisions are collisions where kinetic energy is NOT conserved.

Momentum and Unbalanced Forces (Page 30A+31A) How can momentum be affected or changed? 2) Unbalanced forces: Friction: the force resisting the movement of an object. 4 kinds of friction: static, sliding, fluid, and rolling. Fluid friction: resistive force of an object moving through a fluid. Rolling friction: resistive force of the ground/surface a circular object is rolling on. Air resistance: special type of frictional force on objects traveling through air.

Momentum and Unbalanced Forces (Page 30A+31A) Finding the net force for an object: Add up the arrows that are pointing in the SAME direction. After step 1, subtract the forces pointing in the OPPOSITE direction. The direction of net force is the direction of the greater force.