4.1.1 The Work Done by a Constant Force in One Dimension

Question 1

The Work Done by a Constant Force in One Dimension

Answer 1

• In one dimension, work is the product of the force applied to the object and the displacement of the object: . Work is a scalar, not a vector. The unit of work is the Joule (J): .
• If force and displacement are in the same direction, work is positive. If force and displacement are in opposite directions,work is negative.

Question 2

A block slides 20 meters before it comes to a complete stop. The coefficient of kinetic friction, mk, between the block and the floor is 0.3. The block has a mass of 3 kg. Which of the following is the amount of work done by friction on the block?

Answer 2

−176.4 J

Question 3

A cart weighing 5 N is pushed a distance of 7.5 m by a constant force of 3 N. There is no friction between the cart and the track it is on. Which of the following is the amount of work done by the force?

Answer 3

22.5 J

Question 4

Consider when the displacement and a constant force acting on an object in one dimension result in negative work. Which of the following is correct?

Answer 4

Displacement and the constant force are in opposite directions.

Question 5

A block with a mass of 2 kg sitting at rest on ice is pulled by a rope. The block achieves a velocity of 3 m / s, 4 seconds later, at a point 6 meters to the right of its starting point. If the block’s acceleration was constant and the friction between the ice and block is negligible, which of the following is the amount of work done by the force of the rope as it pulled the block through the first 6 meters?

Answer 5

9 J

Question 6

A meteorite with a mass of 25 kilograms falls to Earth in a direction perpendicular to the Earth’s surface. At t = 0 seconds the meteorite is 1000 meters above the Earth. At t = 2 seconds it is 750 meters above the Earth. Assume the meteorite’s acceleration due to gravity is constant during this time. Which of the following is the amount of work the Earth’s gravitational force has done on the meteorite between t = 0 and t = 2?

Answer 6

61,250 J

Question 7

A block siting on a table moves to the right at a constant speed. The block weighs 5N and the coefficient of kinetic friction, mk, between the block and the table is 0.3. Which of the following is the amount of work done by a force, Fr, as it pulls the block 10m to the right?

Answer 7

15 J

Question 8

The joule is an example of units of work. Which of the following is not a valid unit of work?

Answer 8

lb / s2

Question 9

If work is done by a net force acting on an object, the object must have moved.

Answer 9

true