Question

Тело движется по вертикали под действием силы тяжести. при каком условии работа силы тяжести положительна?

Answer 1

Работа находится по формуле: A=F*S* cosα, при движении вниз cosα=1 работа положительная, при движении вверх, соs =-1 работа отрицательна.

Answer 2

Если на движущееся тело действует только одна сила, то, когда эта сила совершает положительную работу, скорость тела растет. Действительно, в этом случае сила, а значит, и ускорение направлены по скорости, увеличивая ее. Если же сила совершает отрицательную работу, ускорение направлено против скорости и скорость тела убывает.

Answer 3

Conditions for Positive Work by the Force of Gravity

When an object moves vertically under the influence of the force of gravity, the work done by the force of gravity can be positive under certain conditions. The force of gravity always acts in the downward direction, opposite to the direction of motion. The work done by a force is defined as the product of the force and the displacement of the object in the direction of the force.

To determine the conditions for positive work by the force of gravity, we need to consider the relationship between the force of gravity, the displacement of the object, and the angle between them.

1. Positive Work with Displacement in the Same Direction as the Force of Gravity: If the object moves in the same direction as the force of gravity, the work done by the force of gravity is positive. This occurs when the object is moving downward.

2. Positive Work with an Angle Less than 90 Degrees: Even if the object is not moving directly downward, the work done by the force of gravity can still be positive if the angle between the force of gravity and the displacement is less than 90 degrees. In this case, the component of the force of gravity in the direction of motion contributes to positive work.

It's important to note that the work done by the force of gravity can be negative under different conditions. For example, if the object moves upward against the force of gravity or if the angle between the force of gravity and the displacement is greater than 90 degrees, the work done by the force of gravity will be negative.

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