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Potential energy and conservation

Potential energy and conservation

1.[2p]

What makes a force conservative?

Correct
The answer is: The work it does between two points is the same for every path joining them
The answer is: The work it does between two points is the same for every path joining them
The answer is: The work it does between two points is the same for every path joining them

2.[2p]

A ball is released from rest and falls 18 m with no air resistance. What is its speed on arrival, in metres per second?

CorrectNot quite: 18.8

3.[1p]

Kinetic friction is a conservative force.

The answer is: False
Correct

4.[3p]

A pendulum of length 1.2 m is released from rest at 50° to the vertical. What is the speed of the bob at the lowest point, in metres per second?

CorrectNot quite: 2.90

5.[2p]

On a graph of potential energy against position, what does the force on the body equal?

Correct
The answer is: Minus the slope of the curve at that position
The answer is: Minus the slope of the curve at that position
The answer is: Minus the slope of the curve at that position

6.[3p]

A 2.5 kg block slides 6.0 m down a 30° incline with μk=0.20, starting from rest. What is its speed at the bottom, in metres per second?

CorrectNot quite: 6.20

7.[3p]

Which of these statements about potential energy are correct?

Select all that apply

Correct
Correct
Correct
The answer is: Only differences in potential energy affect any physical result, A minimum of the potential energy curve is a point of stable equilibrium, Potential energy belongs to the configuration of an interacting system, not to one body alone

8.[3p]

Match each force to its potential energy function, where it has one.

  • Gravity near the ground

  • Ideal spring

  • Kinetic friction

  • Normal contact force

  • half k x squared

  • mgy

  • none exists

  • none needed, it does no work

Show the answer

Gravity near the ground: mgy Ideal spring: half k x squared Kinetic friction: none exists Normal contact force: none needed, it does no work

9.[2p]

A block is released at the top of a frictionless track, runs down, and enters a vertical loop. Put these speeds in order from largest to smallest.

  1. At the bottom of the drop

  2. At the top of the loop

  3. Back at the starting height on the far side

  4. Halfway up the loop

Show the answer

a, b, c, d