Chapter 5 Flashcards
Newton’s third law
Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first.
Components
Mutually perpendicular vectors, usually horizontal and vertical, whose vector sum is a given vector.
When you push against a wall with your fingers, they bend because they experience a force. Identify this force.
You exert an action force and the wall exerts an equal and opposite reaction force.
A boxer can hit a heavy bag with great force. Why can’t he hit a piece of tissue paper in midair with the same amount of force?
The boxer can only hit the tissue paper with a force as large as the tissue paper can exert on the boxer, and the low-mass tissue can only exert a weak force.
How many forces are required for an interaction?
Two forces, an action and a reaction, are needed for an interaction.
State Newton’s third law of motion.
For every action there is an equal and opposite reaction.
Consider hitting a baseball with a bat. If we call the force on the bat against the ball the action force, identify the reaction force.
The reaction force is the force by the ball on the bat.
If the system of Figure 5.9 is only the orange, is there a net force on the system when the apple pulls?
Yes, there is the action of the apple on the orange.
If the system is considered to be the apple and the orange together (Figure 5.10), is there a net force on the system when the apple pulls (ignoring friction with the floor)?
The net force is zero because the action and reaction forces are equal and opposite.
To produce a net force on a system, must there be an externally applied net force?
Yes, there must be an external net force on the system.
Consider the system of a single football. If you kick it, is there a net force to accelerate the system? If a friend kicks it at the same time with an equal and opposite force, is there a net force to accelerate the system?
If you kick it, there is a net force; if both of you kick it, there is not.
Which of Newton’s three laws focuses on interactions?
Newton’s third law
Can you physically touch a person without that person touching you with the same amount of force?
When you touch a person, they must touch you with an equal and opposite force.
How many forces are required for an interaction?
Two forces, an action and a reaction, are needed for an interaction.
The force that propels a rocket is that provided by _______.
the expelled gas pushing on the rocket.
A Volkswagen Bug and a Volvo truck have a head-on collision. Which statement is true?
The magnitudes of both forces are the same.
State Newton’s third law of motion.
For every action there is an equal and opposite reaction.
Can you physically touch a person without that person touching you with the same amount of force?
No, when you touch a person, they must touch you with an equal and opposite force.
What happens to the magnitude of the normal vector on a block resting on an incline when the angle of the incline increases?
The magnitude of the normal vector decreases.
