Question

a sailor pulls a boat horizontally alongside a dock for 10.0m with a rope angled at 40.0 degrees. He does 766 jules of work.What force did he apply to pull the boat?

Answer 1

Work is equal to force times the distance. However, the distance here is angled horizontally alongside a dock. And so, we have distance times the cos(theta). The equation is W = Fdcos(theta).

W = Fdcos(theta)

766 J = F (10m)cos(10degrees)

F = 77.78 N

Answer 2

Answer:

To pull the boat, he applied a force of 100 N

Explanation:

Work is defined as the force that is applied to a body to move it from one point to another.

When a net force is applied to a mechanical system and it produces displacement, then that force is said to do mechanical work, which can be positive if the system gains energy or negative if the system loses energy.  In other words, you speak of work when there is a force that when applied to a body allows it to move in the direction of the force.

In S.I it is measured in Joule (Newton*meter) and another unit called calorie is commonly used to refer to mechanical work.

The work is calculated as the product of the multiplication of the force by the distance and by the cosine of the angle formed by the force and the displacement experienced by the body. This is represented by: W = F · d · cosα

The force is measured in Newton (N) and the distance traveled in meters.

In this case you know:

• W=766 J
• F=?
• d= 10 m
• α=40 degrees

Replacing:

766 J=F*10m*cos 40

Solving:

$F=\frac{766 J}{10meters*cos 40}$

F= 99.99 N ≅ 100 N

To pull the boat, he applied a force of 100 N