Forces: Pushing and Pulling - First Grade Science
Nothing in our world starts moving, stops moving, changes direction, or speeds up on its own. For an object to move or change its motion, it must be acted upon by a force. In physical science, a force is simply a push or a pull! Every time you open a door, throw a ball, drag a heavy wagon, press a keyboard key, or pedal your bicycle, you are using muscular forces. By studying pushes and pulls, you unlock the physical laws that control how everything in the universe interacts.
The Two Fundamental Forces: Push and Pull
Every physical force can be classified into one of two fundamental actions: pushing or pulling.
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| PUSHES VS. PULLS |
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| PUSH (Moves AWAY from you) PULL (Moves TOWARD you) |
| |
| (YOU) =====[FORCE]=====> [OBJECT] (YOU) <====[FORCE]====== [OBJECT|
| |
| You apply force away from your body You apply force toward your body|
| Examples: Examples: |
| - Kicking a soccer ball forward - Pulling a red wagon behind you|
| - Closing a heavy refrigerator door - Tying your shoelaces |
| - Pushing a friend on a swing - Reeling in a fish on a line |
| - Pressing a button on a remote - Opening a desk drawer |
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What Can Forces Do?
Forces have tremendous power over the physical world. A force can cause five distinct effects on an object's motion.
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| WHAT FORCES CAN DO |
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| 1. START MOTION Make a still object begin moving. |
| 2. STOP MOTION Bring a moving object to a complete halt. |
| 3. SPEED UP Make an already moving object travel faster. |
| 4. SLOW DOWN Reduce the speed of a moving object. |
| 5. CHANGE DIRECTION Deflect a moving object to turn left or right. |
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Starting and Stopping Motion
A soccer ball sits completely motionless on the center line of a grass field. It will sit there forever until a player's foot applies a forward push (a kick). When the ball flies toward the net, the goalkeeper's hands push back against the ball with equal force, absorbing its momentum and stopping the motion instantly!
Changing Direction
Imagine rolling a toy car forward across a hardwood floor. If your partner gently taps the side of the car with a ruler as it rolls past, the car veers sharply to the side. A sideways push changes the direction of motion without stopping the car.
The Size of Forces: Big vs. Small
Forces have both direction and magnitude (strength). You can exert a gentle, small force or an enormous, mighty force.
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| FORCE SIZE AND EFFECT |
| |
| SMALL FORCE BIG FORCE |
| - A gentle tap with a finger. - A mighty kick with full body. |
| - Moves a feather or marble easily. - Moves a heavy bowling ball. |
| - Results in slow speed or short - Results in high speed or long |
| distance traveled. distance traveled. |
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Mass and Force
The heavier an object is (the more mass it has), the more force is required to move it or stop it! You can kick a lightweight beach ball with a tiny push and send it sailing across the lawn. But kicking a heavy medicine ball with that same small push will barely make it budge at all. Heavy objects require much bigger forces to achieve the same acceleration.
Contact Forces vs. Non-Contact Forces
Most forces you use every day require direct physical contact between your body and the object.
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| CONTACT VS. NON-CONTACT FORCES |
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| CONTACT FORCES NON-CONTACT FORCES |
| Objects must physically touch. Force acts across a distance |
| - Hitting a baseball with a bat without touching! |
| - Pushing a swing with hands - GRAVITY: Pulls down to Earth. |
| - Friction of sneakers on floor - MAGNETISM: Attracts iron. |
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Chapter Review Exercises
Question 1: What is the scientific definition of a force?
Question 2: Explain the physical difference between a push and a pull, giving two examples of each from everyday life.
Question 3: List three different ways that applying a force can change the motion of a rolling toy car.
Question 4: Why does it require a much larger force to push a loaded wheelbarrow full of wet garden soil than an empty wheelbarrow?
Solutions and Explanations
Solution 1: In science, a force is a push or a pull applied to an object.
Solution 2: A push is a force that moves an object away from the person or thing applying the force, such as closing a door or kicking a ball. A pull is a force that moves an object toward the person or thing applying the force, such as opening a desk drawer or pulling a wagon.
Solution 3: Applying a force can speed up the car (pushing it from behind), slow it down or stop it (pushing against the front of the car), or change its direction (pushing the car gently from the side).
Solution 4: A loaded wheelbarrow contains much more mass and weight than an empty wheelbarrow. Greater mass has more inertia and requires a significantly larger force to overcome friction and accelerate forward.