Lesson test: Circular dynamics

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Circular dynamics

1.[2p]
A level bend has radius 50 m and $μ_{s} = 0.70$ . What is the fastest speed a car can take it, in metres per second?

CorrectNot quite: 18.5

2.[3p]
A car takes a level bend too fast and leaves the road on the outside. What is the correct description?

The friction available fell short of $m v^{2} / r$ , so the car followed a path of larger radius than the bend

Correct

An outward centrifugal force overcame the friction

The answer is: The friction available fell short of $mv^2/r$, so the car followed a path of larger radius than the bend

The normal force pushed it outward

The answer is: The friction available fell short of $mv^2/r$, so the car followed a path of larger radius than the bend

Its inertia became a force acting outward

The answer is: The friction available fell short of $mv^2/r$, so the car followed a path of larger radius than the bend

3.[3p]
At what angle, in degrees, must a bend of radius 150 m be banked so that a car at 25 m s⁻¹ needs no friction?

CorrectNot quite: 23.0

4.[2p]
What is the minimum speed at the top of a vertical loop of radius 12 m, in metres per second?

CorrectNot quite: 10.85

5.[1p]
The minimum speed at the top of a vertical loop depends on the mass of the body going round it.

True

The answer is: False

False

Correct

6.[3p]
A bob on a 1.5 m string swings as a conical pendulum at 25° to the vertical. What is the period, in seconds?

CorrectNot quite: 2.34

7.[3p]
Which of these are true of the fictitious forces used inside a rotating frame?

Select all that apply

They have no identifiable agent exerting them

Correct

They have no third law partner

Correct

They disappear when the problem is redone in an inertial frame

Correct

They are exerted by the rotation itself on every body

The answer is: They have no identifiable agent exerting them, They have no third law partner, They disappear when the problem is redone in an inertial frame

8.[3p]
Match each circular motion problem to the force that supplies the centripetal requirement.

Car on a level bend
Car on a frictionless banked bend
Conical pendulum
Ball at the top of a vertical loop on a track

the horizontal component of the normal force
the weight plus the track's inward push
the horizontal component of the string tension
friction from the road

Show the answer

Car on a level bend: friction from the road Car on a frictionless banked bend: the horizontal component of the normal force Conical pendulum: the horizontal component of the string tension Ball at the top of a vertical loop on a track: the weight plus the track's inward push

9.[3p]
A 0.50 kg stone is whirled in a vertical circle of radius 0.80 m and passes the lowest point at 6.0 m s⁻¹. What is the string tension there, in newtons?

CorrectNot quite: 27.4

1.[2p] A level bend has radius 50 m and μs=0.70. What is the fastest speed a car can take it, in metres per second?

2.[3p] A car takes a level bend too fast and leaves the road on the outside. What is the correct description?

3.[3p] At what angle, in degrees, must a bend of radius 150 m be banked so that a car at 25 m s⁻¹ needs no friction?

4.[2p] What is the minimum speed at the top of a vertical loop of radius 12 m, in metres per second?

5.[1p] The minimum speed at the top of a vertical loop depends on the mass of the body going round it.

6.[3p] A bob on a 1.5 m string swings as a conical pendulum at 25° to the vertical. What is the period, in seconds?

7.[3p] Which of these are true of the fictitious forces used inside a rotating frame?

8.[3p] Match each circular motion problem to the force that supplies the centripetal requirement.

9.[3p] A 0.50 kg stone is whirled in a vertical circle of radius 0.80 m and passes the lowest point at 6.0 m s⁻¹. What is the string tension there, in newtons?

1.[2p]
A level bend has radius 50 m and $μ_{s} = 0.70$ . What is the fastest speed a car can take it, in metres per second?

2.[3p]
A car takes a level bend too fast and leaves the road on the outside. What is the correct description?

3.[3p]
At what angle, in degrees, must a bend of radius 150 m be banked so that a car at 25 m s⁻¹ needs no friction?

4.[2p]
What is the minimum speed at the top of a vertical loop of radius 12 m, in metres per second?

5.[1p]
The minimum speed at the top of a vertical loop depends on the mass of the body going round it.

6.[3p]
A bob on a 1.5 m string swings as a conical pendulum at 25° to the vertical. What is the period, in seconds?

7.[3p]
Which of these are true of the fictitious forces used inside a rotating frame?

8.[3p]
Match each circular motion problem to the force that supplies the centripetal requirement.

9.[3p]
A 0.50 kg stone is whirled in a vertical circle of radius 0.80 m and passes the lowest point at 6.0 m s⁻¹. What is the string tension there, in newtons?