PHY 101 Chapter 5

Assume that while driving through a curve the friction force that prevents the car from sliding is 12μN. The fastest speed that could be used on the same surface is _______ the original radius.

1.4, sqrt2, or 1.41

An object spinning in a circle with constant speed results in some centripetal acceleration. If the radius is halved, the centripetal acceleration will be _____ times what it was.

2, two, or double

A villain seeks to make a year on Earth's eight times longer, so that one revolution about the sun would then take eight of our current years. To do this, the villain will have to increase the average distance to the sun by a factor of _______ times the Earth's current radius.

4

If a cyclist needs to maintain the same centripetal acceleration but wants to double the speed in the turn, the radius must become _______ times what it was previously.

4 or four

Identify which people are accelerating. Multiple select question. A child on a tricycle traveling in a straight line at constant speed. A child on a swing. A driver cresting a hill at constant speed. A couple on a carousel going around at constant speed. A horse and cowboy galloping up a straight slope at constant speed.

A child on a swing. A driver cresting a hill at constant speed. A couple on a carousel going around at constant speed.

Static force of friction

A frictional force that does not involve motion in the direction of the force.

Geocentric

A model of the universe where the Earth is at the center

Heliocentric

A model of the universe where the sun is at the center

Rank the following situations in order from largest centripetal acceleration (top) to the smallest (bottom).

A speed of 20 m/s and a radius of curvature of 2 m A speed of 10 m/s and a radius of curvature of 1 m A speed of 10 m/s and a radius of curvature of 2 m How to find: a=v^2/r

If the velocity of an object is changing, the object must be _______ .

Accelerating

An object traveling at constant speed has

An undetermined amount of acceleration including possibly zero acceleration

Since the change in the velocity vector is itself a vector it must have a _______ and a ________ .

Blank 1: size or magnitude Blank 2: direction or orientation

If there is a net force acting on an object there will be an acceleration which means that either the speed, the ________ of motion, or both will change.

Direction

Match the quantity with how it is proportional to the force of universal gravitation. Mass Distance Velocity

Directly proportional Inversely proportional to the square Independent

A geocentric model of the universe has the _____ at the center.

Earth

Equation for net force

Fnet=ma

Which of the following are real forces? Multiple select question. Friction force Centripetal force Normal force Gravitational force Mass times acceleration

Friction force Normal force Gravitational force

Sun

Moves through the daytime sky along a predictable path

Planet

Moves through the night sky along a path, but sometimes seems to go backward

Star

Moves through the night sky along a predictable path

While a car makes a certain turn, the frictional force keeping the car from sliding reaches its maximum. If the driver changes the tires so that the coefficient of static friction between the tires and the road is now doubled, which of the following are possible? Multiple select question. Navigate a curve with half the radius. Increase the speed by 1/3. Double the speed. Navigate a curve with twice the radius. Navigate a curve with 1/3 the radius.

Navigate a curve with half the radius. Increase the speed by 1/3. Navigate a curve with twice the radius.

An object traveling at constant velocity has

No acceleration

At the bottom of a Ferris wheel ride the acceleration is straight up. The force that is the largest at this position is the ______ force.

Normal

What does the magnitude of a centripetal force depend on? Multiple select question. Position Radius of curvature Speed Time Mass

Radius of curvature Speed Mass

An object traveling with changing velocity has

Some acceleration

Which of the following statements are correct? The acceleration due to gravity alone is symbolized by G. The universal gravitational constant is symbolized by G. The universal gravitational constant gives the acceleration experienced by a body in free fall. The universal gravitational constant is symbolized by g. The universal gravitational constant states how strongly two objects interact via gravity.

The acceleration due to gravity alone is symbolized by g. The universal gravitational constant is symbolized by G. The universal gravitational constant states how strongly two objects interact via gravity.

Heliocentrism was proposed in ancient times (Aristarchus of Samos was the first to be recored in 270 BCE) but was rejected since it required the Earth to rotate on its axis. If the Earth is a spinning ball, then why do we not feel the wind from that motion (over 1600 km/h at the equator)?

The atmosphere is also rotating.

Which of these situations will result in the force of gravity decreasing according to Newton's law of universal gravitation? Multiple select question. The objects increase their speed The distance between the objects halves The distance between the objects doubles One of the object doubles its mass One of the object loses half its mass

The distance between the objects doubles One of the object loses half its mass

In which of the following cases would the force of gravity increase by a factor of four? Multiple select question. The distance between the objects is halved. The distance between the objects is doubled. One of the masses is quadrupled. Both of the masses are doubled. Both of the masses are quadrupled. One of the masses is doubled.

The distance between the objects is halved. One of the masses is quadrupled. Both of the masses are doubled.

Kinetic force of friction

The frictional force between two objects sliding at the point of contact of their surfaces.

When a curved road is banked, which force or component of a force acts as the centripetal force? Multiple choice question. The horizontal component of the normal force The force of the car's velocity The gravitational force The vertical component of the normal force

The horizontal component of the normal force Reason: The horizontal component of the normal force changes the horizontal velocity's direction, which is centripetal acceleration. The force, or component of a force, that causes the change is termed the centripetal force.

The gravitational acceleration on the surface of the moon is smaller than on the surface of Earth. Choose all the reasons that contribute to this. Multiple select question. The mass of the moon is smaller than that of Earth. The radius of the moon is smaller than that of Earth. The universal gravitational constant is smaller for the moon. The moon is moving faster than the Earth through space.

The mass of the moon is smaller than that of Earth. The radius of the moon is smaller than that of Earth.

Match the location during a Ferris wheel ride with the force that is dominating the net force. At the bottom of the ride. At the top of the ride. Half way up (a quarter turn from the bottom).

The normal force. The weight Some third force (neither weight, nor normal).

Which of the following statements is true about the moon and our communication satellites?

They both have the same ratio of period of rotation, T, and average radius, r. The farther the orbit is from Earth, the longer the orbital period. The closer the orbit is to Earth, the shorter the orbital period.

A planet orbiting the sun has

a force acting centripetally. centripetal acceleration.

Equation for centripetal acceleration

a=v^2/r

By Newton's second law, an object that has a net force acting on it must be _______ .

accelerating

What we often call a centripetal force is simply whichever force or combination of forces that give an object a centripetal _______ .

acceleration

Kepler's second law states that an imaginary line drawn from the sun to any planet moves through equal ________ in equal intervals of time.

areas or distances

The direction of the centripetal acceleration is always toward the _______ of the curve.

center, middle, or inside

Any force, or combination of forces, that causes an object to have a centripetal acceleration is termed a _______ force.

centripetal

The acceleration of an object is its change in velocity divided by the time over which that change occurs. This change can be in the size of the velocity, the direction of the velocity, or both. When the acceleration is only changing the direction of the velocity it is called ______.

centripetal

At the bottom of a Ferris wheel ride, if we set the positive y-axis in the upwards direction Newton's second law gives the equation: N-W = mac, where the centripetal acceleration ac = v2r. If the velocity of the Ferris wheel decreases, the normal force must ______ .

decrease

At the peak of a Ferris wheel ride the centripetal acceleration is downwards, which is parallel to gravity, but opposite the normal force. Because greater speed means greater centripetal acceleration, which means a larger net force, as the speed increases the normal force must ______ .

decrease, diminish, or shrink

Centripetal acceleration is the acceleration which is associated with the change in the _______ of the object's velocity.

direction, bearing, path, trajectory, track, or proclivity

The orbital period of the moon depends primarily on the mass of the ______ .

earth

A planet orbiting the sun does so in an ______ orbit according to Kepler's first law. Since the orbit is not in a straight line, Newton's laws tell us the planet must have a force to cause the _______ acceleration needed to change the direction of the planets. The force that plays this role is gravity.

elliptical, centripetal

The sun exerts a force on a 50-kg Earth dweller of about 0.3 Newtons. The magnitude of the force the Earth dweller exerts on the sun is _______ to that same force since the forces are an action-reaction pair of forces.

equal

The Earth is about 100 times more massive than the moon. The gravitational force exerted by the moon on the Earth must be _____ the force exerted by the Earth on the moon.

equal to

The moon does not hover above the Earth because there is no gravity. In fact, the moon is _______ toward the Earth, but the curvature of the Earth's surface results in the moon never hitting the Earth. This shows that at large velocities, the curative of the Earth's surface is important.

falling, dropping, lowering, plunging, sinking, or accelerating

Kepler found that the model that matched Tycho Brahe's data the best was where the planetary orbits were elliptical with the sun at one _______ of the ellipse.

focus or foci

When an object is traveling in a circle, its velocity is changing directions. This means there must be some centripetal acceleration. If there is some acceleration, then by Newton's second law, there must be a net _________ .

force

A universe model with the Earth at the center, as most early models of the universe speculated, is called a _______ model.

geocentric

A model of the universe in which the sun is the center is called a ________ model and was proposed by Nicolaus Copernicus.

heliocentric

Because Newton's law of Universal Gravitation depends on the distance between the centers of two objects, you would expect g, the acceleration due to gravity, to be ______ at the top of a very high mountain than at sea level.

less

equation for centripetal force

m*(v^2/r)

The magnitude of a centripetal force acting on an object is the object's centripetal acceleration, v2r, times the object's _______ .

mass or m

If an object has zero net force acting on it, then the object Multiple select question. must travel at constant velocity. must change its direction. must travel in a straight line. must speed up or slow down. remains at rest. must travel at constant speed.

must travel at constant velocity. must travel in a straight line. remains at rest. must travel at constant speed.

If an object is changing direction by moving in a circular motion, it must have some Multiple select question. net force centripetal acceleration tangential acceleration changing speed

net force centripetal acceleration

In order for an object to travel in a circle, even at constant speed, there must be a ________ force acting on the object.

net, resultant, nonzero, total, or centripetal

Centripetal acceleration is always Multiple select question. pointed outward from the center of the curve. perpendicular to the tangential velocity. in the same direction as the velocity. in the opposite direction as the velocity. toward the center of the curve.

perpendicular to the tangential velocity. toward the center of the curve.

Ptolemy got rid of concentric sphere's, switching to circular orbits in his model. Further, Ptolemy added epicycles, circles on top of a circular orbit, to account for the ______ motion of the planets.

retrograde

The planets did not simply wander across the night sky as the stars did. The planets sometimes seemed to travel backward for a short while in what is termed ______ motion.

retrograde

When a car rounds a turn on a flat surface without skidding, its acceleration is centripetal and is caused by _______ friction. In this situation, the friction force plays the role of the centripetal force since it causes the centripetal acceleration. (Put one word in the blank.)

static

During some seasons, we can see the moon glow at night. However, the moon is not generating that light on its own; it is reflecting light from the ______ .

sun

Kepler's first law stated that Multiple select question. the planets' orbits were circular. the sun was located at one focus of an ellipse. the Earth was located at one focus of an ellipse. the sun was located at the center of an ellipse. the planet's orbits were elliptical.

the sun was located at one focus of an ellipse. the planet's orbits were elliptical.

Kepler's second law states that an imaginary line drawn from the sun to any planet moves through equal areas in equal intervals of _____ .

time

how to find the change in velocity

v(change)+v(1)=v(2)

At the top of a Ferris wheel ride, the centripetal acceleration is straight downwards. The biggest force acting on the rider is the ________ force.

weight, mg, gravity, or gravitational

At the peak of a Ferris wheel ride the centripetal acceleration is downwards, which is parallel to gravity, but opposite the normal force. The maximum speed a rider can have on the Ferris wheel without requiring a seat belt happens when the normal force is equal to _________ .

zero, 0, or nothing