Question

№1Пуля массой 7,9г вылетает под действием пороховых газов из канала ствола длиной 45 см со скоростью 54 км/ч. Вычислите среднюю силу давления пороховых газов. Трением пули о стенки ствола пренебречь. №2Определите силу сопротивления движению, если вагонетка массой 1 т под действием силы тяги 700 Н приобрела ускорение . №3При трогании с места железнодорожного состава электровоз развивает силу тяги Какое ускорение он при этом сообщит составу массой 3000 т, если сила сопротивления движению

Answer 1

1. $a= \frac{v_{0}^{2}}{2*S} = \frac{225}{0,9} =250m/c^2$

$F=m*a=0,0079*250=1,975H$

2. $F_{tr}=F-m*a=700-1000*0,2=500H$

3. $F-F_{c}=m*a$

$a= \frac{F-F_{c}}{m} = \frac{540000}{3000000} =0,18m/c^2$

Answer 2

Question 1:

The bullet has a mass of 7.9 grams and exits the barrel with a velocity of 54 km/h. We need to calculate the average pressure force exerted by the gunpowder gases.

To calculate the average pressure force, we can use the formula:

Pressure = Force / Area

The force exerted by the gunpowder gases can be calculated using Newton's second law:

Force = Mass x Acceleration

The acceleration can be calculated using the formula:

Acceleration = Change in Velocity / Time

Since we are given the initial velocity and the final velocity is zero (as the bullet exits the barrel), the change in velocity is equal to the initial velocity.

Now, let's calculate the average pressure force:

Step 1: Convert the mass of the bullet from grams to kilograms:

7.9 grams = 0.0079 kilograms

Step 2: Convert the velocity from km/h to m/s:

54 km/h = 15 m/s

Step 3: Calculate the acceleration:

Acceleration = Change in Velocity / Time = 15 m/s / 0.045 s (since the length of the barrel is given as 45 cm, which is equal to 0.45 m, and the velocity is given in km/h)

Step 4: Calculate the force:

Force = Mass x Acceleration = 0.0079 kg x (15 m/s / 0.045 s)

Step 5: Calculate the area:

The area can be calculated using the formula:

Area = π x (radius)^2

Since the bullet is not specified, we will assume a standard bullet diameter of 9 mm, which gives a radius of 4.5 mm or 0.0045 m.

Area = π x (0.0045 m)^2

Step 6: Calculate the average pressure force:

Pressure = Force / Area

Now, let's calculate the values:

Force = 0.0079 kg x (15 m/s / 0.045 s) = 2.63 N

Area = π x (0.0045 m)^2 ≈ 0.0000636 m^2

Pressure = 2.63 N / 0.0000636 m^2 ≈ 41300 Pa

Therefore, the average pressure force exerted by the gunpowder gases is approximately 41300 Pa.