Question

Why is it important to know the direction of the force applied to a moving object and the direction in which the object is moving when determining the work done on the object?
Only the component of the force perpendicular to the motion is used to calculate the work.
If the force acts in the same direction as the motion, then no work is done.
When there is an angle between the two directions, the cosine of the angle must be considered.
A force at a right angle to the motion requires the use of the sine of the angle.

Answer 1

Answer:

C

Explanation:

Answer 2

Answer

(C).

When there is an angle between the two directions, the cosine of the angle must be considered.

Step by step Solution

The work done by a force is defined as the product of the force and the distance traveled in the direction of motion.

The first answer "Only the component of the force perpendicular to the motion is used to calculate the work" is wrong because, the force perpendicular to motion does no work.

The second choice "If the force acts in the same direction as the motion, then no work is done" is wrong because the work in the direction of the force is $W=F\times d$.

Fourth answer "A force at a right angle to the motion requires the use of the sine of the angle" is wrong because the $sin(90)=0$ meaning that there is no work done in the direction perpendicular to the motion.

The third answer" When there is an angle between the two directions, the cosine of the angle must be considered." is correct because the work is calculated using the force in the direction of the motion. The magnitude of this force is $F\times d\times \cos(\theta).$