Physics Unit 6 (Universal Gravitation)

b

A ball is being whirled around a vertical path by a string, as shown below. The net force on the ball is 𝐹𝑛𝑒𝑡 = 𝑇 − 𝑚𝑔, where m is the ball's mass and T is the tension in the rope. Why is the tension force made positive in this equation? A. because the tension force points up B. because the tension force points to the center of the circular path C. because the tension force points perpendicular to the velocity

b; velocity changing direction means acceleration. force and acceleration are directly proportional (Newtons 2nd law)

A biker rides around a curved path. The biker's speed remains constant. The net force on the bicyclist..... A. is nonzero because the bicyclist's velocity is constant. B. is nonzero because the bicyclist's velocity is changing direction. C. is zero because the bicyclist has a fixed speed, so Δ𝑣 = 0.

B

A moon is orbiting a planet at UNIFORM SPEED. Does the moon accelerate as it travels around the planet? A. Yes, because the speed of the moon is constantly changing B. Yes, because the direction of the moons velocity is constantly changing C. No, because the speed of the moon doesn't change D. Not enough info

mass

According to Newton's Law of Universal Gravitation, all mass is attracted to all other _____________

m1 & m2

According to Newton's Law of Universal Gravitation, the force of gravity is directly proportional to _______________

c

According to Newton's universal law of gravitation, the gravitational force between two objects is proportional to:: A). the inverse of their separation distance: 1/r. B). their separation distance: r. C). the inverse square of their separation distance: 1/r^2 D). The square of their separation distance: r^2

mass

According to Newton;s law of universal gravitation, there is a gravitational force attracting all objects that have __________

speed (linear velocity)

An object moving in a circle with UCM has a constant ______________________

newton's law of universal gravitation

Every 2 masses in the universe attract each other with a gravity force (Fg).

the magnitude of velocity stays the same but direction changes which creates acceleration.

Explain why an object with constant UCM & linear speed is accelerating.

positive

Forces pointing INTO the circle (towards the center) are ________________

negative

Forces pointing OUT OF the circle (away from the center) are ____________

a

How do G and g contrast? A). The value of G is always constant, whereas the value of g is only 9.81 near the surface of Earth. B). Both of the values of G (6.67 x 10^11) and g (9.81) apply only near the surface of Earth and change on different planets. C). G (6.67 x 10^11) and g (9.81) are both universal constants that never change.

uniform circular motion

How do you describe the motion of objects moving along a circle with constant linear speed?

static friction

If a car is moving around a circular track.... What provides the net force that accelerates the car toward the center of the circle?

C

In order for an object to turn, it must feel a net force that is directed A. Toward the center of the circular path B. Perpendicularly to the object's velocity C. Both A & B

same direction as force, towards center of circle

In what direction does an object's acceleration point?

toward center

Net Force is always directed ______________________ to/of the circle

inverse square

The force of gravity is proportional to the _________________ of the radius

c (Newton's 3rd law)

The gravitational force on the sun (by the earth) is Fs. Which of the 2 is larger in magnitude? A). l Fs l > l Fe l B). l Fe l > l Fs l C). l Fs l = l Fe l D. Not enough info has been given to compare the two forces

period

The time it takes to go around the circle once

a

The value of G is... A). always 6.67 x 10^11; this value never changes.This answer is correct. B). 6.67 x 10-11 on Earth, but it changes from planet to planet. C). always 9.81. D). 6.67 x 10^11 , but on Earth it is 9.81.

true; newton's 3rd law about equal but opposite forces

True or False (Law of Universal Gravitation) M1 equals the force on m2 even when M1 is bigger than m2. why?

true (the 2 force must be able to cancel each other out)

True or False? The Normal Force (Fn) cannot be bigger than gravity.

true

True or False? The force of gravitational attraction between 2 objects is Directly Proportional to the product of their Masses.

false

True or False? The force of gravitational attraction between 2 objects is Directly proportional to the distance between their centers

false

True or False? The force of gravitational attraction between 2 objects is Inversely proportional to the Distance between their Centers?

false

True or False? The force of gravitational attraction between 2 objects is Inversely proportional to the product of their masses

true

True or False? The force of gravitational attraction between 2 objects is Inversely proportional to the square of the distances between their centers

a

Two objects will be attracted to one another by a gravitational force if.... A). Both objects have mass B). Both objects have electric charge C). both objects are magnetized

perpendicular

Velocity is ___________________ to force

tangent

Velocity is always directed __________________ to the circle

at a 90 degree a radius line

What does "Tangent to the circle" mean?

the separation distance between 2 objects

What does "r" equal in the Universal Gravitational Equation?

an object changing direction

What does this diagram show?

an object slowing down

What does this diagram show?

an object speeding up

What does this diagram show?

gravity/fg

What is keeps objects in orbit?

velocity and force must be parallel

What is required for a moving object to speed up or slow down?

velocity and force must be perpendicular

What is required for a moving object to turn?

tangent

When an object moves in a circle, its velocity is directed __________________ to the circle

c (Newton's 3rd law)

Which object pulls more strongly on the other? (Ignore direction/negative signs.) (A). Object A pulls more strongly on Object B (because object A has more mass). (B). Object B pulls more strongly on Object A (because object B has less mass). (C). The two objects pull with equal strength on each other. (D). Not enough information has been given to solve.

newton's second law. force is directly proportional to acceleration and force is parallel to acceleration.

Why does Net Force and Acceleration always point in the same direction? (Hint: F=ma)

d

You are watching a bicyclist move. How can you tell whether or not the bicyclist feels a centripetal net force? A. If the bicyclist's velocity is changing, then there is a centripetal net force. B. If the bicyclist's speed is changing, then there is a centripetal net force. C. If the bicyclist's speed is constant, then there is a centripetal net force. D. If the bicyclist is turning, then there is a centripetal net force.

centripetal

means "center seeking"