physics Exam 1
Why is force a vector quantity?
A force has a magnitude and a direction.
Rank the velocity of Jake relative to a stationary observer on the ground from fastest to slowest. (Call the direction to the right positive.)
D, C, A, B
Based on the experiment that Dr. Hewitt demonstrated in the video, what factors determine whether the air resistance experienced by a falling object will affect the motion of the object?
The area of the object in relation to the weight of the object determines the air resistance the object experiences. Objects having greater area but smaller weight experience greater effect of air resistance.
Why is a force that is applied for a short time more advantageous in karate?
The average force is increased.
What is the net force on an object in either static or dynamic equilibrium?
The net force is zero.
What relationship did Galileo discover between a ball's acceleration and the steepness of an incline?
The steeper the incline, the greater the acceleration.
An airtanker fighting a forest fire drops flame retardant when flying at a constant horizontal velocity. What will happen to the velocity of the airtanker?
The velocity of the airtanker will increase.
What specific force is accelerating Nellie (Figure 5.23 in the textbook) down the hill? (assume friction to be neglectable)
The x-component of the force of gravity
what did galileo discover about moving bodies and force in his experiments with inclined planes?
in the absence of a retarding force, a body will keep moving at a constant speed in a straight line forever
An impulse can be increased by
increasing the force or increasing the time interval.
The team to win in a tug-of-war is the team that _______.
pushes harder on the floor while holding the rope
When a big fish swims into an oncoming smaller fish and swallows it, the momentum of the two-fish system _______.
remains the same
The force that propels a rocket is that provided by _______.
the expelled gas pushing on the rocket Submit
A ball rolling down an inclined plane each second picks up
the same amount of speed each second
A boxer cannot exert much force on a piece of tissue paper suspended in air because _______.
the tissue paper has too little mass to exert as much force on the boxer's fist Submit
When two vehicles collide, momentum is conserved _______.
whether the collision is elastic or inelastic Submit
What do we call the quantity force multiplied by distance?
work
State the equilibrium rule for forces in symbolic notation
ΣF = 0
What is the acceleration of a car moving along a straight road that increases its speed from 0 to 100 km/h in 10 s?
10 km/h·s
While you are in a bus that moves at 100 km/h, you walk from the back to the front at 10 km/h. What is your speed relative to the road outside?
110km/h
A 12- N book is at rest on a flat table. How many newtons of support force does the table provide?
12 newtons up What is the net force on the book 0 newtons
How far do you travel moving at an average speed of 80 km/h for 30 min?
40 km
If the system is considered to be the apple and the orange together as shown in (Figure 1), identify the force that accelerates the apple-orange system.
A friction force acting on apple's feet.
Give an example in which a force is exerted on an object without doing work on the object.
A satellite is in a circular orbit about Earth.
Briefly, what is science?
A. Science describes the order in nature and the causes of that order. B. Science is a way of knowing about the world and making sense of it. C. Science creates testable laws and theories. D. all the of above D. all of the above
A theory in science is_____.
A. a synthesis of well-tested ideas B. an educated guess C. forever true D. an agreement between trained investigators A. a synthesis of well-tested ideas
What are steps of the scientific method.
A. assembling and organizing facts and checking them against dogma. B. hypothesis, predictions, and experimental findings C. reasoning and derivation and axioms. D. using occam's razor to eliminate excess facts.
Equations in Conceptual Physics are used mainly as _______.
A. experimental tools B. guides to thinking C. recipes to problem solving D. a means of highlighting the mathematical structure of physics B. guides to thinking
what is the language of science?
A. greek B. scientific laws and principles C. mathematics D. English C. mathematics
What is the effect of air resistance on the acceleration of falling objects?
Air resistance decreases the acceleration of falling objects.
What is the role of airbags in vehicles in terms of impulse and momentum?
Airbag extends the time you stop in an accident and thus the force exerted decreases .
What does it mean to say that something is in mechanical equilibrium?
An object in mechanical equilibrium experiences a zero net force.
When you bat a ball, does the ball react at the same time, or a bit later?
At the same time. Submit
Rank the speeds of the airplane across the ground from fastest to slowest.
B, A, C
What did Galileo demonstrate in his Leaning Tower of Pisa experiment?
He demonstrated that light and heavy objects gain the same amount of speed when falling
What did Galileo discover in his legendary experiment on the Leaning Tower of Pisa?
He demonstrated that light and heavy objects gain the same amount of speed when falling.
Distinguish between force and impulse.
Impulse is force times a time interval.
What did Galileo discover about moving bodies and force in his experiments with inclined planes?
In the absence of a retarding force, a body will keep moving at a constant speed in a straight line forever.
If while riding in a smooth-riding train, you toss a coin upward, the coin will normally land ______.
In your hand
What kind of collision, elastic or inelastic, occurs when a large fish swallows a small fish at rest?
Inelastic. The fishes stuck together after the collision. Submit
Fill in the blanks: Newton's first law is often called the law of ____; Newton's second law is the law of ____; and Newton's third law is the law of ____.
Inertia, acceleration, action -reaction Submit
What kind of speed is registered by an automobile speedometer--average speed or instantaneous speed?
Instantaneous speed
What type of path does a moving object follow in the absence of a force?
It continues to move in a straight line at a constant speed.
What is the gain in speed per second for a freely falling object?
It gains approximately 10 m/s.
When are you more aware of motion in a vehicle--when it is moving steadily in a straight line or when it is accelerating?
It is easier to notice acceleration than steady movement in a straight line. In a steadily moving car you would not be aware of the motion if you did not look outside the car.
What does it mean to say that momentum is conserved?
It means momentum does not change.
How does momentum relate to inertia?
Momentum is inertia in motion. Submit
How does Newton's first law of motion relate to Galileo's concept of inertia?
Newton refined Galileo's concept of inertia and made it his first law of motion.
How much force is required to keep a moving hockey puck in motion on a perfectly frictionless surface?
No force is required for continued motion.
Can a net impulse be produced on an automobile if you sit inside and push on the dashboard? Why or why not?
No, because you cannot produce an external force on the car while sitting inside it.
Can you push on a wall without the wall pushing back on you?
No, because your push is part of an interaction with the wall. Submit
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.
Because the forces that act on a cannonball and the recoiling cannon from which it is fired are equal in magnitude, why are the accelerations of both so different?
Remember F=ma, and note that the cannon has a much greater mass than the cannonball, so the cannon accelerates less for the same force.
Why is it advantageous to roll with the punch in boxing?
Rolling with the punch increases contact time, which decreases the force.
A car moving in a circular track at 45 km/h is moving with constant
Speed
How do speed and velocity differ?
Speed is how fast, a scalar quantity. Velocity as a vector quantity states how fast and which direction.
How does the magnitude of acceleration of the rifle compare with the magnitude of acceleration of the bullet, and why?
The acceleration of the rifle is smaller than the acceleration of the bullet. They experience the same magnitude of force, but the mass of the rifle is greater, and so the rifle will experience a smaller acceleration than the bullet.
Why can't a boxer hit a piece of tissue paper in midair with the same amount of force with which he hits a heavy punching bag?
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.
Why are buckets rather than flat paddles used in a Pelton wheel?
The buckets cause the impacting water to bounce, increasing the impulse given to the wheel.
How does the distance traveled by the bullet compare with the distance traveled by the rifle in the same time, and why?
The bullet will travel farther than the rifle because it has a greater magnitude of acceleration.
An old man and his grandchild, both of the same mass, go up the stairs to their first-floor apartment. The child gets to the apartment well before his grandad. Which one delivered more power?
The child
How would the combined momentum of the two cars before collision compare to the momentum of the entangled cars after collision on a perfectly slippery road?
The direction and magnitude remain the same.
Why does a long cannon impart more speed to a cannonball than a small cannon for the same force?
The force is applied for a longer time in the long cannon.
How does a helicopter get its lifting force?
The helicopter exerts downward forces on air; the reaction forces of the air on the helicopter are upward and called lift. Submit
How does the force on the rifle compare with the force on the bullet, and why?
The magnitude of the force of the rifle is equal to the magnitude of force on the bullet and the forces are in the opposite direction, because for every action there is an equal and opposite reaction.
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. Submit
A small car and a large truck have a head-on collision. Which of the following statements is true?
The magnitudes of both forces are the same.
What is the net force on an object that is pulled with 80 to the right and 80 to the left?
The net force is zero newtons.
If two identical sacks are lifted the same vertical distance in the same time, how does the power required for each compare?
The power is the same.
Which has a greater momentum, a heavy truck at rest or a mouse running along the street?
The running mouse.
How much work is done if double the force is applied for half the displacement?
The same
The acceleration of free fall is about 10 m/s2. Why does the unit second appear twice?
The second appears once in the denominator of the unit for speed and once for the interval of time
If the car you are riding comes to a sudden stop, your body moves forward. What is the cause of this motion?
There is no force, your body just continues its motion.
How many forces are required for an interaction?
Two forces, an action and a reaction, are needed for an interaction.
Consider the video demonstration that you just watched. Which of the following changes would make it more likely for the ball to hit both the white can and the green can?
Use a ball that is lighter than the original ball, but still heavier than an empty can. Roll the ball faster.Use a ball that is heavier than the original ball.Roll the ball slower answer is none of the above
The statement "Sue is driving due north at 55 km/h" refers to which physical parameter?
Velocity
Air bags are supplemental protection in cars designed to work best in combination with seat belts. How do these devices protect the driver and passengers?
With these devices, momentum is changed over a longer period of time, with a correspondingly smaller force.
If a car moves with a constant velocity, does it also move with a constant speed?
Yes, because constant velocity requires constant speed in the same direction.
Does twice as much work on a body mean twice as much change in energy?
Yes, it is.
A bowling ball at rest is in equilibrium. Is the ball in equilibrium when it moves at constant speed in a straight-line path?
Yes, the bowling ball is in equilibrium because ΣF = 0.
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.
Earth pulls down on you with a gravitational force that you call your weight. Do you pull up on Earth with the same amount of force?
Yes, you pull up on Earth with the same force. Submit
When you stand at rest on a bathroom scale, how does your weight compare with the support force from the scale?
Your weight is equal in magnitude and opposite in direction to the support force from the scale.
What is the net force on a crate sliding at an unchanging speed when pushed with a steady force of 75 N?
Zero
Newton said that something was needed to change the motion of an object. A clear reading of his first law tells us that what is needed is ______.
a nonzero net force
Galileo discovered that when air resistance can be neglected, all objects fall with the same ______.
acceleration
Force vector components for a sled pulled horizontally by a rope at an upward angle _______.
are normally at right angles to each other
What two units of measurement describe speed?
distance and time.
When a cannonball is fired from a cannon, the momentum of the recoiling cannon is momentarily _______.
equal and opposite to the momentum of the fired cannonball
A boxer rides with the punch so as to reduce ___________.
force
When you lift twice the load twice as high, in half the time, the increase in potential energy is _______.
four times
what did galileo discover in this legendary experiment on the leaning tower of pisa?
galileo found that a heavier stone does not fall significantly faster than the lighter one
what did galileo demonstrate in his leaning tower of pisa experiment?
he demonstrated that light and heavy objects gain the same amount of speed when falling
Cassy can get more force on the bricks she breaks with a blow of her bare hand when _______.
her hand is made to bounce from the bricks
Follow through is important in golf because it results in a greater _______.
impulse on the ball Submit
A slowly moving ship can have a greater momentum than a fast-moving racing car when _______.
its mass times velocity is greater than that of the car
How many forces act on a freely falling object?
one. gravity
The quantity that is called impulse can be measured by the _______.
product of force and time
When a cue ball strikes an 8 ball head-on in a game of pool, the cue ball _______.
transfers its momentum to the 8 ball
When a falling firecracker explodes, the momenta of its pieces _______.
vectorially add up to equal the initial momentum of the firecracker
