Physics: Circular Motion and Gravitation

Question 1

What is centripetal acceleration?

Answer 1

The acceleration directed toward the center of a circular path

Question 2

What is the equation for centripetal acceleration?

Answer 2

a=tv^2/r

centripetal acceleration = (tangential speed)^2/radius of circular path

Question 3

A rope attaches a tire to an overhanging tree limb. A girl swinging on the tire has a centripetal acceleration of 3.0 m/s^2. If the length of rope is 2.1 m, what is the girl’s tangential speed?

Answer 3

2.5 m/s

Question 4

As a young boy swings a yo-yo parallel to the ground and above his head, the yo-yo has a centripetal acceleration of 250 m/s^2. If the yo-yo’s string is 0.50 m long, what is the yo-yo’s tangential speed?

Answer 4

11.18 m/s

Question 5

A dog sits 1.5 m from the center of a merry-go-round. The merry-go-round is set in motion, and the dog’s tangential speed is 1.5 m/s. What is the dog’s centripetal acceleration?

Answer 5

1.5 m/s^2

Question 6

A racecar moving along a circular track has a centripetal acceleration of 15.4 m/s^2. If the car has a tangential speed of 30.0 m/s, what is the distance between the car and the center of the track?

Answer 6

58.4 m

Question 7

What is the equation for centripetal force?

Answer 7

F = m x v^2/r

Centripetal force = mass x (tangential speed)^2/radius of circular path = mass x centripetal acceleration

Question 8

A 2.10 m rope attaches a tire to an overhanging limb. A girl swinging on the tire has a tangential speed of 2.5 m/s. If the magnitude of the centripetal force is 88.0 N, what is the girl’s mass?

Answer 8

29.6 kg

Question 9

A bicyclist is riding at a tangential speed of 13.2 m/s around a circular track.the magnitude of the centripetal force is 377 N, and the combined mass of the bicycle and rider is 86.5 kg. What is the track’s radius?

Answer 9

40.0 m

Question 10

A dog sits 1.50 m from the center of a merry-go-round and revolves at a tangential speed of 1.80 m/s. If the dog’s mass is 18.5 kg, what is the magnitude of the centripetal force on the dog?

Answer 10

39.96 N

Question 11

A 905 kg car travels around a circular track with a radius of 3.25 km. If the magnitude of the centripetal force is 2140 N, what is the car’s speed?

Answer 11

35 m/s

Question 12

What is Newton’s Law of Universal Gravitation?

Answer 12

Fg = G x ((m1 x m2)/r^2)

Gravitational force = gravitational constant x (mass 1 x mass 2/distance between masses^2)

Question 13

What is the gravitational constant?

Answer 13

6.673x10^-11 (N x m^2)/kg^2

Question 14

Where is gravity measured from?

Answer 14

The center of each mass

Question 15

What must the distance between two 0.800 kg balls be if the magnitude of the gravitational force is 8.92x10^-11?

Answer 15

0.69 m

Question 16

Who set out to discover Earth’s density, and paved the way to discover G?

Answer 16

Henry Cavendish

Question 17

How fast does gravity travel?

Answer 17

The speed of light

Question 18

What is Kepler’s First Law of Planetary Motion?

Answer 18

Each planet travels in an elliptical orbit around the sun, and the sun is at one of the focal points.

Question 19

What is Kepler’s Second Law of Planetary Motion?

Answer 19

An imaginary line drawn from the sun to any planet sweeps out equal areas in equal time intervals

Question 20

What is Kepler’s Third Law of Planetary Motion?

Answer 20

The square of a planet’s orbital period (T^2) is proportional to the cube of the average distance (r^3) between the planet and the sun

Question 21

What is the equation for orbital period?

Answer 21

Orbital period = 2 pi x square root ((mean radius^3)/(gravitationalconstant)(mass of central object))

Question 22

What is the equation for orbital speed?

Answer 22

Orbital speed = square root ((gravitational constant)(mass of central object/mean radius))

Question 23

Suppose you know the mean distance between Mercury and the sun and Venus and the sun. You also know the period of Venus’s orbit around the sun. Can you find the period of Mercury’s orbit, and if so, how?

Answer 23

Yes, using Kepler’s Third Law of Planetary Motion.

T1^2/T2^2 = r1^3/r2^3

Question 24

What is torque?

Answer 24

A quantity that measures the ability of a force to rotate an object around its axis

Question 25

What is the equation for torque?

Answer 25

tau = Fd sin theta
torque = force x lever arm

Question 26

What is a lever arm?

Answer 26

the perpendicular distance from the axis of rotation to a line drawn along the direction of the force

Question 27

Find the magnitude of the torque produced by a 3.0 N force applied to a door at a perpendicular distance of 0.25 m from the hinge.

Answer 27

O.75 Nxm

Question 28

If the torque required to loosen a nut on the wheel of a car has a magnitude of 40 Nxm, what minimum force must be exerted by a mechanic at the end of a 30.0 cm wrench to loosen the nut?

Answer 28

133 N

Question 29

What are the six simple machines?

Answer 29

Lever, wedge, inclined plane, wheel and axle, pulley, and screw

Question 30

What are the three simplest simple machines

Answer 30

Lever, inclined plane, wheel and axle (The screw is a mixture of a wheel and axle and an inclined plane, the wedge is two inclined planes stuck together, and pulleys are sets of wheels and axles)

Question 31

What is equation for mechanical advantage?

Answer 31

force out/force in