test 1

6) when the string breaks, what forces should Sylvia tell Jaden are acting on the puck, neglecting air resistance?

- gravitational force - normal force

1) the pair discusses the forces acting on the puck. Jaden mentions several forces. which of the following forces act on the puck

-normal force -air resistance -tension -gravitational force

a book is moved once around the perimeter of a tabletop with dimensions 0.9m x 2.1m. if the book ends up at its initial position, what is its displacement

0 m

3) based on the experiment described in question 1 and the correct choice in that question, what is the value of the maximum tension Tmax that the string can withstand before breaking

Tmax= 294 N

2) based on the information provided in the problem, which equation below would be most useful for finding the acceleration of the speedboat

Vf^2= Vi^2 + 2a(Xf-Xi)

a projectile is launched at some angle to the horizontal with some initial speed Vi, and air resistance is negligible. a) is the projectile a freely falling body? b) what is its acceleration in the vertical direction? c) what is its acceleration in the horizontal direction

a) yes b) -9.8 m/s^2 c) 0

3) based on the correct answer to question 2 above, which result below correctly describes the acceleration of the speedboat in terms of its initial and final velocities and its displacement

a= (Vf^2 - Vi^2/ 2deltaX)

9) what can Jaden say characterizes newtons first law as applied to an object in motion

an object in motion continues moving in the same way unless acted on by an external force

a sailor drops a wrench from the top of a sailboats vertical mast while the boat is moving rapidly and steadily straight forward. where will the wrench hit the deck?

at the base of the mast

2) which of the following geometric models represents a shape that appears in this problem, is related to the base of the fountain, and will be useful for us in solving this problem

circle

in the video, a bowling ball moved in a circular path as a result of a baton tapping on it. the figure below depicts a top down view of the ball as it moves counterclockwise in a circular path. in which direction shown in the figure was the force due to the baton applied to the bowling ball

direction c: perpendicular to the velocity of the ball and radially inward

the figure below shows a birds-eye view of a car going around a highway curve. as the car moves from point 1 to point 2, its speed doubles. which of the vectors a through e shows the cars average acceleration between these two points

e

if a car is traveling westward and slowing down, what is the direction of the force on the car that causes it to slow down

eastward

5) combine the results of questions 3 and 4 to obtain an equation for the height h of the fountain in term of circumference C of the pool and the angle theta.

h= (C/2pi) tan theta

4) consider the correct choice in question 1, where the right triangle is a model containing the height of the fountain as one leg and the angle theta. based on this triangle, what is the correct expression relating the height of the fountain and the radius r of the circular pool

h=rtantheta

a car moving around a circular track with constant speed

has an acceleration directed toward the center of its path

the manager of a department store is pushing horizontally with a force of magnitude 200 N on a box of shirts. the box is sliding across the horizontal floor with a forward acceleration. nothing else touches the box. what must be true about the magnitude of the force of kinetic friction acting on the box

it is less than 200 N

a baseball is thrown from the outfield toward the catcher. when the ball reaches its highest point, which statement is true

its velocity is perpendicular to its acceleration

5) which of these expressions should Jaden tell Sylvia is the correct expression for centripetal force, Fc?

m(v^2/r)

can the equations of kinematics be used in a situation in which the acceleration varies in time

no

if an equation is dimensionally correct, does that mean that the equation must be true

no

must two quantities have the same dimensions if you are dividing them

no

must two quantities have the same dimensions if you are multiplying them

no

7) neglecting air resistance, what horizontal forces should Jaden tell Sylvia act on the once the string breaks

no horizontal forces act on the puck

2) air resistance is often ignored in physics problems. how can Sylvia explain to Jaden the reason that air resistance is ignored

often air resistance has a negligible effect on the final answer, so we can use a simplified model in which we assume no air resistance

1) the problem suggests that an initial experiment was performed in which the object was hung from a stationary vertical string. as the mass of the object is slowly increased, the string breaks when the mass is mbreak= 30 kg. what analysis model can be used to correctly describe the object hanging from the unbroken string for a fixed value of the mass

particle in equilibrium

2) now imagine that the object is set into circular motion on the table as in the figure. what analysis model can be used to correctly describe the object in this situation

particle in uniform circular motion

1) which of the following analysis models best represents the motion of the boat during its displacement

particle under constant acceleration

the figure below depicts a top down view of the bowling ball moving in a circular path. which of the paths in the figure best represents the motion of the bowling ball after the baton stopped tapping it

path c: it moves in a straight line

3) consider the correct choice in question 2, where the circle is a model for the round pool. what is the correct expression for the radius r of the circle in terms of its circumference C

r=(C/2pi)

A rubber ball is dropped onto the floor. What force causes the ball to bounce?

reaction force of the floor

1) which one of the following geometric models represents a shape that appears in this problem, contains the measurement h, and will therefore be useful for us in solving this problem

right triangle

a coin placed 29.2 cm from the center of a rotating, horizontal turntable slips when its speed is 50.8 cm/s. what force causes the centripetal acceleration when the coin is stationary relative to the turntable?

static friction

8) what can Sylvia say about the direction of motion of the puck just before the string breaks

tangent to the circle

4) Jaden recalls that the centripetal force is a convent name for the radial component of the sum of all the real forces acting on the body. which of the forces acting on the puck should Sylvia say is radial

tension

when applying the equations of kinematics for an object moving in one dimension, which of the following statements must be true

the acceleration of the object must remain constant

A student throws a heavy red ball horizontally from a balcony of a tall building with an initial speed v0. At the same time, a second student drops a lighter blue ball from the same balcony. Neglecting air resistance, which statement is true?

the balls reach the ground at the same instant

which statement best describes how the magnitude and direction the bowling ball's velocity changed with each tap of the baton

the direction of velocity changed due to the force applied by the baton, but the magnitude of the velocity did not significantly change

a large crate of mass m is place on the flatbed of a truck but not tied down. as the truck accelerates forward with acceleration a, the crate remains at rest relative to the truck. what force causes the crate to accelerate

the friction force

describe the path of a moving body in the event that its acceleration is constant in magnitude at all times and perpendicular to the velocity

the object will move in a circle at a constant speed

describe the path of a moving body in the event that its acceleration is constant in magnitude at all times and parallel to the velocity

the object will move in a straight line at a changing speed

10) what can Sylvia conclude about the motion of the puck once the string has broken, neglecting air resistance and friction

the puck will continue moving in a straight horizontal line forever, because no horizontal forces are acting on the puck

11) consider again the simulation. if the tension in the string were doubled, Jaden and Sylvia wonder how the radius of the circular path the puck follows would have to change for the tangential speed to remain the same. which of the following is correct

the radius decreases by half

a juggler throws a bowling pin straight up in the air. after the pin leaves his hand and while it is in the air, which statements are true

the velocity of the pin is opposite its acceleration on the way up

4) based on the correct choice in question 2, apply newtons second law to the rotating object and solve for the max speed that the object can have before the string breaks. select the Appropriate result from the choices below

vmax= sqrt (TmaxR/m)

what is the reason for the ball's path, found above, after the baton stops tapping it

when the baton no longer applied a force, there was essentially no net force on the bowling ball

can they be used when the acceleration is zero

yes

if an equation is not dimensionally correct, does that mean that the equation cannot be true

yes

must two quantities have the same dimensions if you are adding them

yes

must two quantities have the same dimensions if you are equating them

yes

must two quantities have the same dimensions if you are subtracting them

yes