Question

Через неподвижный блок переброшена невесомая нерастяжимая нить,к концам которой прикреплены два груза одинаковой массы М=9 кг. На один из грузов поставлен небольшой грузик массой m=2 кг, после чего вся система пришла в движение.Определить с какой силой N давит этот грузик на свою опору.Трение в блоке пренебречь.

Answer 1

1 )найдем ускорение грузов

а*(m+M+M)=m*g
a=m*g/(m+2*M)=10*2/(2+18)=1 м/с
2) так как маденький груз движется с ускорением направленным вниз то

P=m*g-m*a=m*(g-a)=2*8=16 Н

Ответ P=16 Н

Answer 2

Problem Analysis

We have a system consisting of a fixed block with an inextensible and weightless string passing through it. Two identical masses, each with a mass of M = 9 kg, are attached to the ends of the string. A small mass, m = 2 kg, is placed on one of the masses. The entire system is set in motion, and we need to determine the force N with which this small mass presses against its support.

Solution

To solve this problem, we can use Newton's second law of motion, which states that the net force acting on an object is equal to the product of its mass and acceleration. In this case, the small mass m will experience two forces: the force of gravity and the tension in the string.

Let's break down the solution into steps:

1. Calculate the force of gravity acting on the small mass m: - The force of gravity is given by the formula F_gravity = m * g, where g is the acceleration due to gravity (approximately 9.8 m/s^2). - Substituting the given values, we have F_gravity = 2 kg * 9.8 m/s^2 = 19.6 N.

2. Determine the acceleration of the system: - Since the masses are connected by an inextensible string, the acceleration of the system will be the same for all masses. - We can calculate the acceleration using the formula a = F_net / (2M), where F_net is the net force acting on the system and 2M is the total mass of the system (2 masses of M each). - The net force acting on the system is equal to the force of gravity acting on the small mass m, which is 19.6 N. - Substituting the values, we have a = 19.6 N / (2 * 9 kg) = 1.09 m/s^2.

3. Calculate the tension in the string: - The tension in the string is the force that keeps the masses connected and causes the system to accelerate. - We can calculate the tension using the formula T = 2M * a, where 2M is the total mass of the system and a is the acceleration. - Substituting the values, we have T = 2 * 9 kg * 1.09 m/s^2 = 19.62 N.

4. Determine the force N exerted by the small mass on its support: - Since the small mass is in contact with its support, it exerts a force on it. - This force is equal in magnitude and opposite in direction to the tension in the string. - Therefore, the force N exerted by the small mass on its support is equal to the tension in the string, which is 19.62 N.

Answer

The force N exerted by the small mass on its support is 19.62 N.