# Ch. 5 Test

a corresponding reaction force
If there is one force present, what else is always present?
the other surface simultaneously exerts the same amount of force on you
You cannot exert a force on a floor or any other surface unless what happens?
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you can not push harder on one hand than the other
What can you not do when your hands are in contact with each other?
g (the acceleration of gravity)
When a ball is bounced on a floor, the acceleration on the ball between bounces is eqaul to what?
the floor
Where does the force the casues a ball to bounce off the floor come from?
No
Can a boxer exert a 60N force on a piece of paper?
the ground
In a tug-of-war, what does the winning team exert the most force on?
1.) there is an interaction between you and the wall and 2.) the wall pushes back on you
When you push against a wall, nothing can happen unless what two things happen?
2 objects
What does an interaction require?
simaltaneously
How must a pair of action-reaction forces always occur?
equal in magnitude and opposite in direction
For every action force, there must be a reaction force that is what?
the cannon ball
When a cannonball is fired from a cannon, what undergoes the greatest acceleration?
no
Are the accelerations of a pair of action-reaction forces always equal?
yes
Are the forces of a pair of action-reaction forces always equal?
the ground pushes the horse to the left
When a horse walks and he pushes on the ground to the left, how does the ground push?
the ball pulls the Earth upward
As a dropped ball falls toward the surface of the Earth there is an action reaction force pulling the ball to the ground. What is the reaction force?
296N (W=Fg: 80kg(3.7 m/s²) = 296N)
An astronaut with a mass of 80kg weighs 800N on Earth. What is his weight on Mars where the acceleration of gravity is 3.7 m/s²?
net force
What must there be to produce acceleration to a system?
When the force exerted on the tires of a car directly accelerates it along a road, what is the force exerted by?
gravity
With negligible air resistance, once a tossed ball leaves your hand, what is the only force that acts on it?
force
What is acceleration directly proportional to?
mass
What is acceleration inversly proportional to?
1.) zero 2.) equal to its weight 3.) equal to its weight minus air drag
When a ball falls downward, what are the three things its net force may be equal to?
the same
The impact force between to objects is what for both objects?
it is the same for both of them
When an aardvark and a Land Rover travelling at the same speed collide head on, what is the impact force?
its mass is 1/2 the mass of the other cart
A pair of carts with a compressed spring between them is set in motion. If onr cart moves at twice the speed of the other, what is its mass?
the object with the lower mass
After a head-on collision between two different mass objects traveling at the same speed, which object undergoes the greatest change in velocity?
the aardvark
An aardvark and a Land Rover traveling at the same speed have a head on collision. Which one undergoes the greatest change in velocity?
50N
If one end of a rope is pulled with a force of 50N, while the other end is pulled with 50N, what is the tension of the rope?
300N
What is the tension in a rope that is pulled by two people, each exerting 300N of force?
4m
Two objects, one twice as massive as the other, are pulling on a rope toward each other on a frictionless surface and are 12 m apart. They meet face to face. What is the distance the more massive person moved?
1/2 the acceleration
What does double the mass eqaul
1.) make a vector sketch and label all given and known information 2.) identify know and unknown (what you want to find) 3.) use the provided equations to find the unknown
What are the three steps to solve vector problems?
equal to the speed the snowflake
A vertically falling snow makes slanted 45 degree streaks on the side of the window of a moving car. What is the speed of the car?
magnitude
When a person stands on a horizontal surface, the person’s weight and the noraml force have the same what?
the tension in each rope is more than half her weight
When a person hangs suspeneded from a pair of ropes that are not vertical, what is the tension in each rope?
no, it does not change
Does the force due to gravity that acts on a block of ice that slides down an icy ramp change as the angle of the ramp changes?
yes, it decreases
Does the normal force that acts on a block of ice that slides on a ramp change as the the slope of the ramp increases?
when friction equals the parallel force of the weight
When does a shoe on an inclined surface barely remain at rest?
the weight remains the same
As the sloped surface supporting a shoe become steeper, what happens to the shoe’s weight?
the friction increase
As the sloped surface supporting a shoe become steeper, what happens to the friction needed to keep the shoe at rest?
the normal force becomes less
As the sloped surface supporting a shoe become steeper, what happens to the normal force?
the force vectors add up to 0
When an ape is suspended at rest by holding rope with one hand and the side of the cage with the other, all of the force vectors add up to what?
If acceleration is 0, what must the sum of all forces equal?
no, the horizontal component remains the same
When a ball is tossed upward at an angle (disregarding air resistance), does the horizontal component of the initial velocity vector change?
yes, the vertical component increases up to the top of the flight, then decreases at the same rate to the ground
When a ball is tossed upward at an angle (disregarding air resistance), does the vertical component of the initial velocity vector change?
5 units (solve using Pythagorean theorem: a² + b² = c²)
What is the resultant of a vertical vector of 3 units combined with a horizontal vector of 4 units?
5 units (solve using cos60° × 10)
What is the magnitude of the vertical component of a 10 unit vector 60° clockwise from the vertical?
70.7 km/h (solve by doing cos45° × 100)
An airplane travels at 100 km/h toward the northeast (45° north of east). What is the velocity due north?
316 km/h (solve using Pythagorean theorem: a² + b² = c²)
The air speed of an airplane is 300 km/h. It is caught in a 100 km/h crosswind (90° to its path in the air). What is the across the ground below?
the state of motion of an object
A force is a push or pull that is required to the change of what?
two forces
A force interaction requires at least what?
opposite in direction, equal in magnitude, and occurs at the same time
Whenever one object exerts a force on a second object, the second object exerts a force on the first that is what?
the highway pushing back on the wheels of the truck
The force that propels a heavy truck along a highway is provided by what?
the same
Each pulls on the moon with a certain force relative to this force, the full of the moon on earth is what?
the boulder pulling up on the earth
A boulder falls due to gravity. What is the reaction to the force on the boulder?
the foot
If action is a foot kicking a soccer ball, the reaction is an equal force on what?
equal
Two identical carts have a compressed spring between them. When the spring is released, the carts recoil from each other with oppositely directed accelerations that are what?
4000 N
An axe is swung against a tree with a blow of 4000 N. What is the force that acts on the axe during this event?
the ejected air
When the neck of an air-filled balloon is untied and air escapes, the balloon shoots through the air. The force that proves the balloon is provided by what?
move downward
When you jump vertically upward, strictly speaking, what do you cause the Earth to do?
the same as; more than
A mosquito has a collision with the windshield of a massive high-speed truck. The force of impact on the mosquito is ___________ the force on the truck, and the acceleration of the mosquito is ___________ the deceleration of the truck.
the truck
A massive truck and a golf cart have a head-on collision with equal amounts of force. The least amount of acceleration occurs for which object?
becasue the water exerts a net forward force
When a squid pushed against water, why does the squid move forward?
when it is kicked by two feet with equal and opposite amounts of force
When can the net force of a kicked soccer ball be zero?
the mass of what’s being hit
The amount of force with which a boxer’s punch lands depends on what?
45°
You can run horizontally at 4 m/s in a vertically falling rain that falls at 4 m/s. Relative to you, the raindrops are facing at an angle of what?
80 N
The resultant of a 30 N force and a 40 N force cannot possibly be what?
in the rope with the smallest angle to the vertical
When Nellie Newton hangs by a pair of ropes at different angles to the vertical, in which rope is the rope tension greater?
it gets progressively less as the slope of the ramp increases
What happens to the normal force that acts on a block of ice that slides on a ramp?
the component of mg parallel to the surface
A shoe on an inclined surface barely remains at rest when friction equals what?
equal to 45°
Horizontal and vertical components of velocity are equal when the projection angle is what?

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