Concave lens cause rays to ____

If a cars velocity is slowing down is it considered a positive or negative acceleration?

Natali [406]

Answer:

Negative

Explanation:

Observe that the object below moves in the positive direction with a changing velocity. An object which moves in the positive direction has a positive velocity. If the object is slowing down then its acceleration vector is directed in the opposite direction as its motion (in this case, a negative acceleration).

4 0

3 years ago

A supersonic nozzle is also a convergent–divergent duct, which is fed by a large reservoir at the inlet to the nozzle. In the re

Lady_Fox [76]

Answer:

155.38424 K

2.2721 kg/m³

Explanation:

$P_1$ = Pressure at reservoir = 10 atm

$T_1$ = Temperature at reservoir = 300 K

$P_2$ = Pressure at exit = 1 atm

$T_2$ = Temperature at exit

$R_s$ = Mass-specific gas constant = 287 J/kgK

$\gamma$ = Specific heat ratio = 1.4 for air

For isentropic flow

$\frac{T_2}{T_1}=\frac{P_2}{P_1}^{\frac{\gamma-1}{\gamma}}\\\Rightarrow T_2=T_1\times \frac{P_2}{P_1}^{\frac{\gamma-1}{\gamma}}\\\Rightarrow T_2=00\times \left(\frac{1}{10}\right)^{\frac{1.4-1}{1.4}}\\\Rightarrow T_2=155.38424\ K$

The temperature of the flow at the exit is 155.38424 K

From the ideal equation density is given by

$\rho_2=\frac{P_2}{R_sT_2}\\\Rightarrow \rho=\frac{1\times 101325}{287\times 155.38424}\\\Rightarrow \rho=2.2721\ kg/m^3$

The density of the flow at the exit is 2.2721 kg/m³

4 0

2 years ago

A bridge to be fabricated of steel girders is designed to be 500 m long and 12 m wide at ambient temperature (assumed 20°C). Exp

andrew-mc [135]

Answer:

23

21.7391304348 m

Explanation:

L = Initial length = 500 m

$\Delta T$ = Change in temperature = 40-(-35)

$\alpha$ = Coefficient of thermal expansion = $12\times 10^{-6}\ /^{\circ}C$

Change in length is given by

$\Delta L=L\alpha \Delta T\\\Rightarrow \Delta L=500\times 12\times 10^{-6}\times (40-(-35))\\\Rightarrow \Delta L=0.45\ m$

The change in length is 0.45 m

The number of joints would be

$n=\dfrac{0.45}{0.02}\\\Rightarrow n=22.5\\\Rightarrow n\approx 23$

The number of joints is 23

Each bridge section length would be

$\dfrac{L}{n}=\dfrac{500}{23}=21.7391304348\ m$

The length of each bridge section would be 21.7391304348 m

4 0

3 years ago

The ____ force is the sum of all the forces that act upon each other

Pavel [41]

the resultant force

5 0

3 years ago

Read 2 more answers

An engine pulls a train of 20 freight cars, each having a mass of 4.900 × 104 kg, with a constant force. The cars move from rest

bixtya [17]

Answer:

The force with which the tenth car pulls the eleventh one is called tension and is equal to:

T=119715.91 N

Explanation:

The force (F) with which the tenth car pulls the eleventh one is called tension and its direction is the X-direction or horizontal. According to Newton's Second Law of motion:

$\sum F=ma$

That is, the force of the car is equal to the acceleration (a) times its mass (m). The acceleration is the change in the velocity divided by the time (i is for initial and f is for final).

$a=\frac{v_f-v_i}{t_f-t_f}$

Using Newton's second law:

To find the forces, you have to solve the equilibrium in X-direction:

$\sum F_x=T=ma_x$

Now you can substitute the accelertion in terms of velocity and time:

$\sumF_x=T=ma_x=m\frac{v_f-v_i}{t_f-t_i}$

Solve the equation using the data from the problem, remember that the mass of the object is 10 times the mass of one car because the 10th car has to pull all the other cars:

$T=m\frac{v_f-v_i}{t_f-t_i}=(10)*(4.900 \times 10^4 kg)(\frac{4.3 m/s}{17.60s})\\T=119715.91 N$

4 0

3 years ago

Concave lens cause rays to _____.