Vocabulary
A push or a pull on an object.
Force
What is a force?
A force is a push or a pull.
Do balanced or unbalanced forces cause the motion of an object to change?
Unbalanced Forces
What does Newton’s 1st Law say about objects at rest?
Newton’s 1st Law says that an object at rest will stay at rest unless acted on by an unbalanced force.
What force keeps you on the ground?
Gravity
Two or more equal forces acting in opposite directions on an object, resulting in a net force of zero and no change in the object's motion
Balanced Forces
Name two examples of forces you experience every day.
Gravity pulling you toward the ground and friction slowing you down when you walk etc..
Two students are pushing on opposite sides of a shopping cart with the same amount of force. What will happen to the motion of the cart?
The cart will not move because the forces are balanced.
What does Newton’s 1st Law say about objects in motion?
Newton’s 1st Law says that an object in motion will stay in motion at the same speed and in the same direction unless acted on by an unbalanced force.
What force slows down moving objects when they rub together?
Friction
an object at rest will stay at rest, and an object in motion will continue moving in the same direction and at the same speed unless acted upon by an outside force
Newton's 1st Law of Motion
What unit is used to measure force?
Newton
A book is resting on a table without moving. The force of gravity pulls it down, and the table pushes up with an equal force. What type of forces are acting on the book, and what happens to its motion?
The forces are balanced, so the book stays still.
According to Newton’s First Law (the Law of Inertia), what happens when you push a shopping cart that is not moving?
The shopping cart starts to move forward because an unbalanced force (your push) changes its state of motion.
A skateboarder pushes off the ground and starts rolling. Which forces are acting on the skateboard?
Gravity pulls it down, friction slows it down, and the push (applied force) makes it move forward.
the force that resists the motion of objects when they are in contact with each other
Friction
A tug-of-war is happening between two teams. One team pulls harder than the other. What kind of force is acting on the rope, and what will happen to it?
An unbalanced force is acting on the rope, so it will move toward the team pulling harder.
The force exerted by water and air on the skier is 50 N to the left, and the force exerted by the boat on the skier is 40 N to the right. How will these unbalanced forces affect the motion of the skier?
The skier will accelerate backward to his left.
You are riding in a car, and it suddenly stops. What happens to your body, and how does Newton’s 1st Law explain it?
Your body keeps moving forward because of inertia — Newton’s 1st Law says an object in motion will stay in motion unless acted on by an unbalanced force (like the seatbelt).
Explain how seatbelts help demonstrate Newton’s 1st Law.
Seatbelts stop your body from continuing to move forward when a car suddenly stops, showing that objects in motion stay in motion unless acted on by an unbalanced force.
The tendency of an object to remain stationary or in motion.
Inertia
Explain how you could tell if multiple forces acting on an object are balanced or unbalanced.
You can tell by observing the object’s motion — if it stays still or moves at a constant speed, the forces are balanced. If it starts moving, speeds up, slows down, or changes direction, the forces are unbalanced.
Eva’s blueberries weigh slightly more than Morgan’s raspberries. The left pan is moving downward while the right pan moves upward. Three blueberries fall from the left pan. Now, the right pan weighs more than the left pan. How will the motion of the balance change after the blueberries fall?
The right pan will move downward, and the left pan will move upward.
Give a real-life example that shows Newton’s 1st Law in action and explain how it applies.
When a soccer ball is kicked, it keeps rolling across the field until friction and gravity slow it down and stop it. This shows Newton’s 1st Law because the ball would keep moving in a straight line unless unbalanced forces acted on it. etc..
When a ball is thrown into the air, how do the forces acting on it change as it goes up and comes back down?
As the ball goes up, gravity pulls it down and slows it. At the top, it stops for a moment, then gravity makes it speed up as it falls back down.