Forces and Interactions
Newton's 3rd Law
Action and Reaction Diff Mass
Horse and Cart
Misc
100
A force is always part of a mutual action that involves_____________ ____________.
Another force
100
Consider hitting a baseball with a bat. If we call the force the bat exerts against the ball the action force, identify the reaction force.
A baseball hits the bat
100
True or False : Action and Reaction forces cancel each other when either of the forces is external to the system being considered.
False. They do NOT cancel each other.
100
How many horizontal forces are exerted on the cart? What is the horizontal net force on the cart?
Two: P and f , net force is P-f
100
What is the net force on a falling 100-N barrel hitting a pavement with 5000 N of force?
Fnet =5000 N -100 N =4900 N upward (for the 5000 N force on the pavement is matched by 5000 N acting on the barrel)
200
An _____________ is a mutual action between one thing and another.
interaction
200
How do we know what is an action force versus a reaction force?
Identify the objects. Action - object A exerts a force on object B. Reaction- object B exerts a force on object A.
200
If the world pulls you downward against your chair, what is the reaction force?
Reaction is you pulling upward on the world.
200
How many horizontal forces are exerted on the horse-cart system? What is the horizontal net force on the horse-cart system?
Two; F and f ; net force is F-f
200
When 56-kg Diane on rollerskates pushes against a wall with a force of 28 N, she accelerates away from the wall. Show that Diane's recoil acceleration is 0.50m/s2.
a=F/m
28N/56kg =0.50m/s2
300
When hammering an object, what forces are exerted?
The hammer hitting the nail and the nail hitting the hammer.
300
When you walk on a floor what pushes you along?
The floor
300
When a cannon is fired, are the forces on the cannonball and on the cannon equal in magnitude? Are the accelerations of the two equal?
The forces are equal. The acceleration is unequal.
300
How does a horse-cart system accelerate?
If the horse in the horse-cart system pushes the ground with a greater force than it pulls on the cart, there is a net force on the horse, and the horse-cart system accelerates.
300
When you get up from a sitting position , do your feet push against the floor with a force equal to, more than, or less than your weight?
More than your weight, bc you accelerate upward and push against the floor to do so.
400
Can an action force exist without a reaction force?
NO.
400
What are two types of forces ?
Action and Reaction
400
When can two kicks on a dodge ball produce a net force of zero on the ball?
When both kicks are simultaneous, equal magnitude, and opposite in direction.
400
A small car bumps into a van at rest in a parking lot. Upon which vehicle is the force of impact greater?
Impact force is the same on both.
400
Amanda looks at a 1.0 kg bag of jellybeans resting on a table.
Calculate the amount of force that the table exerts on the bag of jellybeans.
10N
1 kg = 10 N of force
500
When a hammer exerts a force on a nail, how does this amount of force compare with that on the hammer?
Both are the same.
500
State Newton's third law of motion.
Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first object.
500
Why don't the enormous number of inter-atomic forces inside a baseball accelerate the baseball?
They act within system, so there is no net force on system
500
A small car bumps into a van at rest in a parking lot.Which vehicle undergoes the greater change in acceleration?
Car has less, so greater acceleration for car.
500
True or False: A rocketship is pushed forward by gases that are forced out the back of the ship.
true