Balanced and Unbalanced Forces
Which of the following examples of motion describes a balanced force?
A stationary car or an accelerating car?
A stationary car.
Define Gravity.
Force that attracts objects to move towards the center of the earth, moon, or other planet
What are Newton's 3 Laws of Motion?
1. Inertia (objects will stay at rest unless acted on by an unbalanced force).
2. F=ma (The force required to accelerate an object depends on its mass)
3. Action-Reaction (Every action has an equal and opposite reaction)
What two variables must be included when describing velocity?
Speed and Direction
Describe the slope of an object accelerating on a speed/time graph.
Positive slope.
What is the net force of a balanced object?
0N
Describe two factors that can affect the strength of gravity.
Distance between objects and mass of the objects.
Provide evidence for the following claim: Rockets can launch into space.
Newton's 3rd Law: Action Reaction
The downward force of the fire from the exhaust propels the rocket upward into space.
True or False: Acceleration is not only speeding up.
True
Reasoning: Acceleration is any change in velocity (speeding up, slowing down, changing direction).
Describe the slope of an object that is stationary on a distance/time graph.
No slope- a straight line
A skiier is moving downhill. The normal force is 80N and gravity is pulling the skiier at 80N.
The resistance of the skiier is 10N and the fluid friction is allowing the skiier to accelerate at 100N.
What is the Net Force of this unbalanced force?
90N
True or False: Mass changes as objects move from planet to planet.
If False, explain why.
False- Mass stays the same no matter where is objected in located in the universe. Mass refers to the amount of atoms within the object. Weight however can change as the formula for weight is W=mg (Weight=Mass x Force of Gravity)
Students are completing a lab pulling three different objects with spring scales. They make the following claim: The amount of force required to move an object is directly related to its mass.
What evidence can you use to support this?
Newton's 2nd Law F=ma
The mass determines how much force is necessary to accelerate the object.
How would you describe the motion of an object that is moving with constant positive velocity?
Describe the slope of an object that has a constant velocity on a speed/time graph
No slope- A straight line
A soccer player kicks a ball with 200N of applied forced toward the left. object falling toward Earth with gravity pulling at 90N. Air resistance is acting again the object with 20N.
Describe the motion and net force of the object.
The object is falling down and to left with a net force of 130N
Which combination would produce the greatest force of gravity?
Two 20g objects 100 miles apart
Two 100g objects 5cm apart
One 50g object and One 70g object 5cm apart
Two 100g objects 5 cm apart
*Most mass with least distance in between.
Describe a demonstration that models inertia.
Newton's 1st Law: Objects will stay at rest or in constant motion unless acted on by an unbalanced force.
*Answers will vary-Examples could include:
-Inertia in a Cup (Penny and note card)
-Newton's Cradle
-Sports
-Any demo that shows a balanced force changing velocity (accelerating)
How would you describe on object that is moving with constant speed, but non-constant velocity?
The object is moving at the same speed but changing directions.
Describe the slope of an object that is returning back to its starting point on a distance/ time graph.
A negative slope.
How can an object in motion be considered balanced?
Moving with a constant velocity.
How can you provide evidence for the following claim:
An asteroid changes velocity due to Earth's gravitational force.
As the asteroid moves closer to Earth, the gravitational force from Earth is greater than the asteroid. The pull of gravity from Earth changes the speed and direction of the asteroid.
Timothy is pulling a wagon with bricks to construct a new house. He is on a time constraint and needs to keep the same speed to get to the house on time. Right before he does, more bricks get added to his wagon-just in case.
What does Timothy need to do to ensure he gets to the house in the SAME amount of time he planned?
Newton's 2nd Law: F=ma
Apply more force to cause more acceleration for more mass.
Describe the motion of an object with a constant deceleration?
The object is slowing down at the same rate.
Example: A car is going 40 mph per hour, but then decelerates 5 mph every second to slow down and reach the speed limit.
Describe the slope of an object that is moving with non-constant acceleration on a distance/time graph.
A positive non-linear slope (exponential)