Forces: What are Forces and Types of Forces PDF

# What are Forces? - A force is a push or pull on an object. - Forces are applied by another object. - If an object is left alone, it won't change. - An object can change if it's pushed or pulled. **Example:** If you leave a ball on the floor, it will stay there until something pushes (kicks) it...

# What are Forces? - A force is a push or pull on an object. - Forces are applied by another object. - If an object is left alone, it won't change. - An object can change if it's pushed or pulled. **Example:** If you leave a ball on the floor, it will stay there until something pushes (kicks) it or pull (grabs) it. ## Types of Forces - **Push:** - Push a door closed. - **Pull:** - Pull open a door. ## Contact Forces Contact forces happen when there is contact between objects. Contact forces include: ### Applied - Applied forces are exerted by an object or a person onto a different object by pushing or pulling. - **Example:** Both people are applying a force to the cabinent. ### Friction - Friction is the resistance that one object has when in contact with another object or surface. - **Example:** There is not a lot of friction when you skate on ice with ice skates. There is a lot of friction if you tried skating with boots on rocks. ### Tension - Tension is exerted by pulling on a string or rope that is connected to an object. - **Example:** These kids are exerting tension on the tug-of-war rope. They are pulling the rope that is being held by the other side. ### Elastic - Elastic forces happen when a spring (or something elastic like a rubber band) is stretched or compressed. - **Example:** A child that is jumping on a trampoline stretches the springs, but the trampoline springs will compress back to its original state through elastic forces.) ## Contact Forces Jigsaw Project You will become an expert in one topic of contact forces. You will get together with other students to plan, create, and demonstrate your contact force topic. Then you will present your expertise to a different small group (called the jigsaw group) that your teacher will create. Each small group will have a different expert to share their knowledge (one member will be a friction expert, another will be an elastic expert, etc.) #### **Follow these steps to complete the project:** **Step 1:** With your small group members, use the planning paper on the next page to research some examples of your contact force. For example, if you are working on friction, write down different real-life examples of how friction opposes the movement of objects. **Step 2:** Create a small poster to describe your contact force. Your poster must include: - Use a regular 8.5 x 11 piece of paper. - A title (this is the name of your contact force) - A short description of your force in your own words - 3 pictures or drawings of this this contact force. **Step 3:** Discuss and plan how you will demonstrate an example of your contact force to the jigsaw small group. **Step 4:** On presentation day, you will present your expert knowledge to your jigsaw group. - First you will share your mini poster and the information on it. - Then you will demonstrate your contact force to the group. ## Project Planning Page - The contact force I am becoming an expert in is: - The members of my expert group are: - Here are real-life examples of this type of contact force: - This is how our group decided we will demonstrate our contact force: - The materials that I will need to bring for the demonstration are: ## Applying Forces We know that contact forces happen between objects that touch each other. We can apply a contact force in many ways like: - Stretching - Pulling - Squeezing - Pushing ### Underneath each picture, write down if the object is being stretched, pulled, squeezed, or pushed. ## Everyday Forces Activity - You will be conducting a descriptive investigation about everyday forces around you. - A descriptive investigation requires you to make important observations. - In this experiment, you will walk around your school to carefully observe where contact forces occur. - You will draw a picture and describe how the force is exerted. #### You'll need: - Your observation page. - A pencil - Pencil crayons #### What to do: **Step 1:** Walk around your school. Carefully observe how an object might have a contact force applied to it. (Can it be squeezed? What happens? Can it be pushed? What happens? Etc.) **Step 2:** On your observation page, it's important that you draw a detailed picture and include a sort description of how the force is applied. You should use words like push, pull, squeeze or compress, or stretch. **Step 3:** Finally, go back over your observations and label them with the correct contact force: - Was it an applied force? - Was there a lot of friction? - Was there tension? - Was it an elastic force? ## Everyday Forces Activity | IMAGE OF THE FORCE | DESCRIPTION OF FORCE | TYPE OF CONTACT FORCE | |---|---|---| |---|---|---| |---|---|---| |---|---|---| |---|---|---| ## Describing Forces - We can describe the strength of a force using words like stronger or weaker, and larger or smaller. - For example, “That team was much stronger than ours during the tug-of-war challenge” or “You must pluck the guitar strings lightly to make a gentle sound.” - We can also use vocabulary to describe the direction of a force onto an object like: - Upward - Downward - From the left - From the right - From both sides - From all directions - For example, when talking about the direction of a force, we can say “she pinched the button from both sides”, or “he pushed the cabinet from the right side.” ### Underneath each picture, write down which direction the force is being exerted. Use the list above to help you: ## STOP Check Your Understanding Let's stop and check your understanding so far in the unit. Remember to answer the questions in complete sentences. 1. Describe what forces are in your own words: 2. What are the four types of contact forces? 3. What are four ways that you could apply a force? 4. Describe an everyday situation where you encounter lots of friction? 5. Tying your shoelaces up can be classified as which type of force? 6. Blowing up a balloon is an example of which kind of contact force? ## Forces Can Cause Change - When you push, pull, stretch, or squeeze an object, you can change the object in different ways. - Forces can cause an object to change its' shape, size, and movement. **Examples:** - A soccer ball shape changes slightly on impact, when you kick it. It changed from a circle shape to an oval shape for a second. - When you blow up a balloon, the rubber is stretched, it becomes larger, and it is easier to move. ## Changing Movement Not only can you make an object move with force, but you can make it move in many ways. - When you apply a force to an object (like pushing, pulling, squeezing, or stretching) you can cause the object to: - Speed up - Slow down - Start moving - Stop moving - Change direction ## Changing Objects Experiment - In this experiment, you will be performing little experiments and exploring how forces can change the shape and size of objects. - While you explore and investigate each item, make sure you fill out your experiment log page. #### You'll need your own: - Spring - Rubber band - Stress ball - Clay/Plasticine - Deflated balloon - Thin plastic bottle - Marshmallow - Sponge #### What to do: - **Step 1:** Exploring one item at a time, you will be testing how the object changes when you apply different forces to it. - **Step 2:** Write down your observations with each item in the chart. - **Step 3:** Repeat your experiments until you have tested each item. ## Changing Objects Experiment | ITEM | Does the object change size and/or shape when you stretch it? What happens? | Does the object change size, and/ or shape when you squeeze/compress it? What happens? | |---|---|---| | Clay | | | | Elastic band | | | | Marshmallow | | | | Spring | | | | Stress ball | | | | Plastic bottle | | | | Sponge | | | ## Marbles Activity - Today you will be playing a game of marbles to explore how different strengths of forces can affect an object's direction. - Together in small groups, you will play a game of marbles on a carpeted surface first, and then on a smooth surface. #### You'll need: - Masking tape or yarn - 14 Marbles (all the same size) - 1 larger marble (this is the shooter marble) - Access to a carpeted surface and smooth floor #### What to do: - **Step 1:** Using tape or yarn, make a circle that is 90cm wide in diameter on a carpet. - **Step 2:** Take the 14 marbles and drop them in the center of the circle, about 15cm away from the ground. The marbles should scatter but no leave the circle. If any escape the circle, just drop them back in - **Step 3:** One student will take the larger marble and sue it to try and knock out as many marbles out of the circle as they can in one shot. The student must flick the marble using their thumb and index finger. Any marbles that are knocked out of the circle now belong to that student and each marble is worth 1 point. Take turns until all the marbles are our of the circle. Count up the points. - **Step 4:** Play the game again, this time on a smooth floor. Drop the marbles near the surface so that they don't bounce or crack. - **Step 5:** When finished both games, answer the reflection questions on the next page. ## Marbles Games 1. How was playing marbles on the carpet different than playing on the floor? 2. Which game had the most friction? 3. In which game did you have to use a stronger force to knock the marbles out? Why? 4. Describe what happens to the smaller marbles when you shoot the larger marble at it. 5. Name a surface that would make playing marbles much harder than the carpeted area. Why do you think it would be much harder?