Question

Сани с седоками общей массой 100 кг съезжают с горы высотой 8 м и длиной 100 м. Какова работа силы сопротивления движению санок, если в конце горы они достигли скорости 10 м/с, а начальная скорость была равна нулю? Ответ в кДж

Answer 1

Изменение полной механической энергии равно работе силы трения:
A=m*g*h-m*V^2/2=m*(g*h-0,5*V^2)=100*(10*8-0,5*100)=3000 Н 

Answer 2

Calculating Work Done by Resistive Force

To calculate the work done by the resistive force on the sled with riders, we can use the work-energy principle, which states that the work done on an object is equal to the change in its kinetic energy.

Given: - Mass of the sled with riders (m) = 100 kg - Height of the hill (h) = 8 m - Length of the hill (d) = 100 m - Initial velocity (u) = 0 m/s - Final velocity (v) = 10 m/s

First, we can calculate the change in potential energy and kinetic energy to find the work done by the resistive force.

Change in Potential Energy

The change in potential energy is given by the formula: ΔPE = mgh where: - m = mass - g = acceleration due to gravity (approximately 9.81 m/s^2) - h = height

Substitute the given values: ΔPE = 100 kg * 9.81 m/s^2 * 8 m ΔPE = 78480 J

Change in Kinetic Energy

The change in kinetic energy is given by the formula: ΔKE = 0.5 * m * (v^2 - u^2) where: - m = mass - v = final velocity - u = initial velocity

Substitute the given values: ΔKE = 0.5 * 100 kg * (10 m/s)^2 ΔKE = 50000 J

Work Done by Resistive Force

Using the work-energy principle: Work = ΔKE + ΔPE Work = 50000 J + 78480 J Work = 128480 J

Therefore, the work done by the resistive force on the sled with riders is 128480 J.