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AP Physics Ch 6-7

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Section 1

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Susie sees Billy and feels some indescribable force that is pulling her toward him. She feels her 70 kg mass being pulled toward his 90 kg mass ever so slightly even though he is 4 m away from her. Assuming this indescribable force is gravity, what is its magnitude?

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Mar 14, 2020

Cards (41)

Section 1

(41 cards)

Susie sees Billy and feels some indescribable force that is pulling her toward him. She feels her 70 kg mass being pulled toward his 90 kg mass ever so slightly even though he is 4 m away from her. Assuming this indescribable force is gravity, what is its magnitude?

Front

2.62 x 10-8 N

Back

A regulation basketball is a thin spherical shell of 24.26 cm in diameter and a mass of 0.625 kg. What is its moment of inertia about an axis that passes through its center?

Front

.006 kg m2 (Using the spherical shell about its diameter equation).

Back

The door to my classroom is 90 cm wide, 2 m high, and 4.2 cm thick; has a mass of 27 kg; and pivots on frictionless hinges. If a "door closer" were attached to the door at the top of the door frame and the door is open and at rest it will exert a torque of 5.2 N*m. What is the least amount of force needed to keep the door open?

Front

5.78 N

Back

angular velocity

Front

rad/s

Back

What is the rotational motion equivalent of: velocity (v)

Front

angular velocity (ω)

Back

Define frequency and period using your own words. What are the correct labels for each?

Front

Frequency is the number of times you go around in 1 second (rps- rotations per second). Period is how long it takes you to go around 1 time (seconds).

Back

What is critical speed?

Front

The speed at which an object must go to complete a vertical circle

Back

A 6.5 m diameter merry go round is turning with a 6.0 second period. What is the speed of a child on the rim?

Front

3.4 m/s

Back

torque

Front

N*m

Back

The Flash runs in a circular, 80 m diameter track 6 times (beginning and ending at the same location) in 3.5 seconds. What is his angular speed in rad/s?

Front

10.8 rad/s (diameter does not play a factor since we are looking at angular speed, not tangential speed).

Back

What are two ways that you change planet Earth so that the acceleration due to gravity is greater?

Front

Make Earth smaller and have more mass

Back

What is the rotational motion equivalent of: Force (F)

Front

Torque τ

Back

A playground toy has four seats, each with a mass of 5.0 kg, attached to a very light, 1.5 m long rods attached to an axis from which they spin. If 3 children, each with a mass of about 18 kg, sit in 3 different seats, what is the moment of inertia about the rotation axis?

Front

166.5 kg m2

Back

angular acceleration

Front

rad/s^2

Back

What is the center of gravity?

Front

The center of gravity (or center of mass) used in calculations where you assume all of the mass of an object is located in one single point.

Back

Describe how you would find the velocity of an object attached to a rope that is moving over a pulley (without slipping).

Front

The object is going to have the same velocity as the rope that it is attached to. The rope is going to have the same velocity as the velocity found at the rim of the pulley. So all you really need is to find the tangential velocity of the pulley.

Back

A basketball is spun on an axle through its center by an electric motor. What torque must the motor supply to take the ball from 0 to 2,000 rmp in 5.0 s? (Assume the same mass and diameter from the question above.)

Front

0.26 N m (Using same moment of inertia from previous question)

Back

In speed skating the track has a straight sections and semicircles 16 m in diameter. Assume that a 65 kg skater goes around the turn at a constant 12 m/s. What is the centripetal force on the skater?

Front

1170 N

Back

This morning I was coasting down a level part of road going approximately 30 mph. If my tires have a diameter of 55.88 cm, what is the angular speed of my tires? What is the speed of the outer rim of my tire as it is 55.88 cm above the road? What is the speed of the outer rim of my tire as it is making contact with the road?

Front

48 rad/s; 26.82 m/s; 0 m/s

Back

A fast pitch softball player does a "windmill" pitch by moving her hand through a circular arc to pitch a ball at 75 mph. The 0.2 kg ball is 0.5 m from the pivot point at her shoulder. At the lowest point of the circle, the ball has reached its maximum speed. At the bottom of the circle, just before she releases the ball, what is the centripetal acceleration? What is the centripetal force at this same point?

Front

2248.25 m/s2; 449 N

Back

Russel's outstretched arm measures 72 cm from his shoulders to his fingertips and weighs 45N. a) Find his arm's center of mass if he is holding a .42 kg football. b) What is the gravitational torque on his arm while holding the football (computed around the shoulder joint).

Front

a) .39m b) 19 N*m

Back

What is the rotational motion equivalent of: acceleration (a)

Front

angular acceleration α

Back

period

Front

seconds

Back

A typical hard disk in a computer spins at 5400 rpm What is its frequency in revolutions/second? What is the period in seconds?

Front

90 rps; .011 s

Back

Which of the following is NOT constant with uniform circular motion

Front

Velocity Acceleration Force (None of these are constant since the direction of their vector is constantly changing)

Back

T/F: The angular velocity on any part of the blade of a wind turbine is the same but the angular speeds will vary.

Front

True

Back

angular displacement

Front

rad

Back

Two cylinders of equal mass and diameter are rolling down an incline. If one is a solid cylinder and the other has more of a hoop shape (hollow in the middle), which shape would you expect to reach the end of the incline first. Explain your answer.

Front

The cylinder that is solid (not the hoop) will finish this race first. The reason being that its mass is found closer to the center upon which it rotates as compared to the hoop where all of its mass is located far from the center.

Back

What is a satellite?

Front

An object that orbits another object and only have gravity/weight force acting on it.

Back

What is the rotational motion equivalent of: displacement (d)

Front

Angular Displacement (θ)

Back

What is the net torque on the bar pictured below? LOLZ probably look at the picture on the study guide. This is #9 from Ch. 7

Front

5.5 N*m

Back

moment of inertia

Front

kg*m^2

Back

What is the rotational motion equivalent of: speed (s)

Front

angular speed (v)

Back

The crankshaft in a race car goes from rest to 3000 rpm in 2.0 s. a) What is the crankshaft's angular acceleration b) How many revolutions does it make while reaching 3000 rpm?

Front

a) 157 rad/s2 b) 50 revolutions

Back

What is the free fall acceleration at the surface of Mars with a radius of 6.779 x 106 m and a mass of 6.39 x 1023 kg?

Front

3.7 m/s2

Back

A frictionless pulley has a mass of 1.5 kg and a radius of .45 m has a rope going over it. The tension in the rope is 10 N going clockwise and 12 N going counterclockwise. What is the angular acceleration of the pulley?

Front

5.9 rad/s2 (Using I = ½ MR2 since it is moving about its center and is solid).

Back

What does it mean for an object to have a positive angular velocity in rotational motion?

Front

If the angular velocity (or acceleration) is positive it is moving in the counterclockwise direction. Negative would mean that it's moving clockwise.

Back

An old fashioned vinyl record rotates on a turntable at 45 rpm. What is the angular speed in rad/s? What is the period of the motion?

Front

4.71 rad/s; 1.33 s

Back

What force(s) act on an object in orbit?

Front

ONLY GRAVITY

Back

The International Space Station is in a 250 mile high orbit. What are the station's orbital period and speed? (Earth's radius = 6.371x106 m, Earth's mass = 5.972x1024 kg)

Front

Period = 5061.3 s Speed = 7907.8 m/s

Back

What is centripetal force? What is centrifugal force? Which of these is NOT an actual force, why?

Front

Centripetal force is the center seeking net force that occurs when an object is in uniform circular motion. Centrifugal force occurs because your inertia, which is not a force, causes you to continue to go straight. Since inertia is not a force, centrifugal force is NOT an actual force.

Back