work physics

Which sets of units represent legitimate units for the quantity work? Circle all correct answers a. Joule b. N x m c. Foot x pound d. kg x m/sec e. kg x m/sec^2 f. kg x m^2/sec^2

Answer: A, B, C, F

Work is a ______________; a + or - sign on a work value indicates information about _______. a. vector; the direction of the work vector b. scalar; the direction of the work vector c. vector; whether the work adds or removes energy from the object d. scalar; whether the work adds or removes energy from the object

Answer: D

A waiter carries a tray full of meals across a dining room at a constant speed.

No Explanation: There is a upward force applied to the tray but the tray moves horizontally. Upward forces do not cause horizontal displacement.

A teacher applies a force to a wall and becomes exhausted.

No Explanation: While there is a force, the force does not cause a displacement. of any object.

A rolling marble hits a note card and moves it across a table.

Yes Explanation: The marble applies a force to the note card to move it across the table. This is work.

A shot-putter launches the shot.

Yes Explanation: The shot-putter applies a force to displace the shot from a compressed arm position to an outstretched arm position.

A weightlifter lifts a barbell above her head.

Yes Explanation: There is a force applied to the barbell and the force causes a displacement of the barbell.