Question

Тело без начальной скорости падает с высоты H= 20м. Определите скорость тела на высоте h=15м. Сопротивлением движению пренебречь. Коэффициент g принять равным 10Н/кг.

Answer 1

K=mv2/2
П=mgh
v=K/П
m-сокращаются 

Answer 2

Problem Analysis

We are given that an object is falling from a height of 20m without any initial velocity. We need to determine the velocity of the object when it reaches a height of 15m. We can neglect air resistance in this scenario, and the acceleration due to gravity is given as 10N/kg.

Solution

To solve this problem, we can use the principle of conservation of mechanical energy. The mechanical energy of the object is conserved as it falls, meaning the sum of its potential energy and kinetic energy remains constant.

At the initial height of 20m, the object has potential energy, which can be calculated using the formula: potential energy = mass x gravity x height. Since the mass of the object is not given, we can assume it to be 1kg for simplicity.

Let's calculate the potential energy at the initial height: Potential energy at height H = mass x gravity x height = 1kg x 10N/kg x 20m = 200J.

At a height of 15m, the object will have both potential energy and kinetic energy. The potential energy at this height can be calculated in the same way as before: Potential energy at height h = mass x gravity x height = 1kg x 10N/kg x 15m = 150J.

Since the mechanical energy is conserved, the sum of the potential energy and kinetic energy at height h will be equal to the initial potential energy.

Let's calculate the kinetic energy at height h: Initial potential energy = Potential energy at height h + Kinetic energy at height h.

Rearranging the equation, we can solve for the kinetic energy at height h: Kinetic energy at height h = Initial potential energy - Potential energy at height h.

Substituting the values, we get: Kinetic energy at height h = 200J - 150J = 50J.

The kinetic energy can be calculated using the formula: kinetic energy = 0.5 x mass x velocity^2.

Let's solve for the velocity at height h: 50J = 0.5 x mass x velocity^2.

Since the mass is assumed to be 1kg, we can simplify the equation: 50J = 0.5 x 1kg x velocity^2.

Simplifying further, we get: 50J = 0.5 x velocity^2.

Dividing both sides by 0.5, we have: 100J = velocity^2.

Taking the square root of both sides, we get: velocity = √(100J) = 10m/s.

Therefore, the velocity of the object at a height of 15m is 10m/s.

Answer

The velocity of the object at a height of 15m is 10m/s.