Bellringer Get out essentials and turn to homework Read article on your desk forces Write questions and answers in isn

Day 1 Motion, force, and mass Force and Motion

Standard: 8-5 The student will demonstrate an understanding of the effects of forces on the motion of an object. (Physical Science)

8-5.4 Predict how varying the amount of force or mass will affect the motion of an object

Motion What is motion? –A change in the position of an object over time. How do you know something has moved? –You use a reference point! A stationary (not moving) object such as a tree, street sign, or a line on the road. Did the beaver move?

What causes an object to move? –A FORCE! –ALL motion is due to forces acting on objects! What is a force? –A push or a pull FORCE MOTION

Can more than one force act on an object at the same time? #2 #3 #1 YES! Example: Gravity is pulling you down to Earth, the ground is supporting you, and your legs moving you forward as you run during PE. The total combination of the forces acting on an object is called NET FORCE.

Mass Mass is how much matter is in something. –You can physically touch matter. –The more matter there is, the more something will weigh. –It is not the same as weight -amount of gravity pulling on an object. It’s harder to make a large object move or change the speed and direction of it when it’s moving.

Questions What happens when I throw a baseball and a bowling ball with the same force? Which one speeds up faster and why?

Lab: Motion After a Collision p443 in text book How is it possible for a 70-kg football player to knock down a 110-kg player? The smaller player usually must be running faster. Mass makes a difference when two objects collide, but the speed of the objects also matters. Explore the behavior of colliding objects in this lab.

Lab Directions: Space yourself about 6 feet away from a partner. 1.Slowly roll a tennis ball on the floor toward your partner. Have your partner roll a tennis ball quickly into the tennis ball. What happens? 2.Slowly roll a base ball on the floor toward your partner. Have your partner roll a base ball quickly into the tennis ball. What happens? 3.Roll one tennis ball and the other student roll to hit the tennis ball with your ball what happened to both tennis balls 4. Roll the base ball and hit it with the tennis ball and record what happens

Lab: Findings What happened when you rolled the fast moving tennis ball into the slow moving tennis ball? What happened when you rolled the fast moving baseball into the slow moving tennis ball? What happened when you rolled two tennis balls into each other at the same speed?

Day 2 Force, mass and motion Force and Motion

Force Review If an object is in motion and more force is applied to it, the object will begin moving faster. If two objects have the same mass and a greater force is applied to one of the objects, the object which receives the greater force will change speeds more quickly. –Example – hit a ball harder it speeds up

Force Review If an object must be slowed down quickly, the force applied to the object must be greater than what is needed for a gradual slowing down. –Example: bicycle brakes

Force Review Varying the amount of force applied to a moving object can also change the direction that the object is moving more or less quickly. –Example – baseball will change direction when hit by a bat

Mass Review If a heavy (more massive) object is in motion, more force must be applied to get the object moving faster. If the same force is applied to two objects, the object with the smaller mass will change speeds more quickly. –For example if a baseball and a bowling ball are thrown with the same force the baseball will speed up faster.

Mass Review In order to slow down or stop a heavier (more massive) object, the force on that object must be greater than for a less massive object. –Example – a small car will slow down more quickly than a large truck It is more difficult to change the direction of a heavy moving object, than one that is lighter in mass.

.

How much force gravity pulls on an object The amount of matter in an object Weight depends on location of object Always constant (same) no matter the location. Newtons (N) g, kg, mg scaleBalance Yes on Earth - once you leave Earth your weight will change, but your mass will remain the same

Lab: marble Forces and Motion page 471 Lean 2 meter sticks parallel, less than a marble width apart on 3 stacked books. This is your ramp. Tap a marble so it rolls up the ramp. Measure how far up the ramp it travels before rolling back. Repeat step 2 using 2 books, 1 book, 0 books. The same person should tap with the same force each time. Make a table to record the motion of the marble for each ramp height.

Forces and Motion Lab Marble Roll Height INCHESINCHES Number of Books Stacked

Question What would happen if the ramp were perfectly smooth and level?

Exit Slip Explain how changes in mass effect the motion of an object.

Day 3 Force, mass and motion review Balanced and Unbalanced forces Force and Motion

Review True or False If an object is in motion and more force is applied to it, the object will begin moving faster.

True or False If an object must be slowed down quickly, the force applied to the object must be greater than what is needed for gradual slowing down or stop

Mass If a heavy (more massive) object is in motion, more force must be applied to get the object moving______________. (Faster/slower)

True or False It is more difficult to change the direction of a heavy moving object, than one that is lighter in mass.

Indicator: Analyze the resulting effect of balanced and unbalanced forces on an object’s motion in terms of magnitude and direction.

Balanced Forces A balanced force is one in which the net force equals ZERO. Do you think there will be any motion? –NO! Examples: 25 Newtons

Unbalanced Forces An unbalanced force is one in which the net force is greater than zero. Do you think there will be any motion? –YES! Examples: 25 Newtons40 Newtons 2 N 50 N

Only an _______________ force can change the motion of an object. Example: Your dog can cause you to move if he pulls with enough force. –His force is greater than the force you’re using to stay in place

What would happen if an unbalanced force acted on an object that’s already in motion? It will change the speed or direction of the object. Example: Your little brother is riding his tricycle. You run up behind him and give him a push. –Your force adds to the existing force causing him to speed up.

Unbalanced forces can act in the same direction. Example: You’re pushing a cabinet across the room with a force of 15 N. You’re friend is pulling with a force of 10 N. What is the NET FORCE? What direction is the cabinet moving? 15 Newtons10 Newtons

Unbalanced forces can act in opposite directions. Example: Two dogs are tugging on a rope. One dog pulls with a force of 20N and the other pulls with a force of 25N. What is the NET FORCE? What direction is the rope moving? 25 Newtons20 Newtons When you have opposing forces, the direction the object moves is in the same direction as the larger force.