1. It is an object's tendency to resist a change in motion.

A motor is used to lift a 10 kg mass 2 m above the ground in 4 s. If the power input to the motor is 100 W. what is the efficien

Bad White [126]

Answer:

98%

Explanation:

Given parameters

Mass of motor = 10kg

Height = 2m

Time = 2s

Power input = 100w

Unknown

Efficiency = ?

Solution

Efficiency is the percentage of the power output to the power input.

Power is the rate at which work is done.

Power output = mass x g x height / time

g is the acceleration due to gravity

Power output = 10x 2 x 9.8 / 2 = 98W

Efficiency = power output/ power input x 100

Efficiency = 98/100 x 100 = 98%

7 0

2 years ago

For what angle of incidence at the first mirror will this ray strike the midpoint of the second mirror (which is s=29.0cm long)

Lesechka [4]

The question is missing a diagram of the ray reflection. I attached a diagram which comes from a similar question in the answer section. The full question should be as follows:

Two plane mirrors intersect at right angles. A laser beam strikes the first of them at a point d = 10.0cmfrom their point of intersection, as shown in the figure. For what angle of incidence at the first mirror will this ray strike the midpoint of the second mirror (which is s=29.0cm long) after reflecting from the first mirror?

Answer:

34.6°

Explanation:

To strike the midpoint of the second mirror, the ray light will have to travel half of the distance vertically

i.e. 29/2 = 14.5

We can solve this through trigonometry.

Let the angle between the ray and the vertical plane mirror is known as α

tan α = 10/14.5

α = $tan^{-1} (10/14.5)$ = 34.6°

The angle of incidence is the angle between the ray and the normal line of the mirror.

Let angle of incidence of first mirror be β

β = α = 34.6

6 0

3 years ago

What is the speed of sound in air at 50°F (in ft/s)?

gizmo_the_mogwai [7]

Answer:

Speed of air = 1106.38 ft/s

Explanation:

Speed of sound in air with temperature

$v_{air}=331.3\sqrt{1+\frac{T}{273.15}} \\$

Here speed is in m/s and T is in celcius scale.

T = 50°F

$T=(50-32)\times \frac{5}{9}=10^0C \\$

Substituting

$v_{air}=331.3\sqrt{1+\frac{10}{273.15}}=337.31m/s \\$

Now we need to convert m/s in to ft/s.

1 m = 3.28 ft

Substituting

$v_{air}=337.31\times 3.28=1106.38ft/s \\$

Speed of air = 1106.38 ft/s

6 0

3 years ago

A golfer hits her tee-shot due north towards the fairway. Her shot has an initial velocity of 60 m/s. A 15 m/s wind is blowing i

vovangra [49]

Answer:

$c=71.4m/s$

$\theta=8.54\textdegree$

Explanation:

From the question we are told that

Initial velocity of 60 m/s

Wind speed $V_w= 15 m/s \angle 45 \textdegree$

Generally Resolving vector mathematically

$sin(45\textdegree)15=10.6\\cos(45\textdegree)15=10.6$

Generally the equation Pythagoras theorem is given mathematically by

$c^2=a^2+b^2$

$c^2=10.6^2 +(10.6+60)^2$

$c=\sqrt{10.6^2 +(10.6+60)^2}$

Therefore Resultant velocity (m/s)

$c=71.4m/s$

b)Resultant direction

Generally the equation for solving Resultant direction

$\theta=tan^-1(\frac{y}{x})$

Therefore

$\theta=tan^-1(\frac{10.6}{70.6})$

$\theta=8.54\textdegree$

7 0

2 years ago

A single strain gage has a nominal resistance of 120 ohm. For a quarter bridge with 120 ohm fixed resistors, strain gauge factor

natita [175]

Answer:

Output voltage is 1.507 mV

Solution:

As per the question:

Nominal resistance, R = $120\Omega$

Fixed resistance, R = $120\Omega$

Gauge Factor, G.F = 2.01

Supply Voltage, $V_{s} = 3\ V$

Strain, $\epsilon = 1000\times 10^{-6}\ strain$

Now,

To calculate the output voltage, $V_{o}$ :

WE know that strain is given by:

$\epsilon = \frac{(R + R')^{2}V_{o}}{RR'V_{s}\times G.F}$

Thus

$V_{o} = \frac{RR'V_{s}\epsilon \times G.F}{(R + R')^{2}}$

Now, substituting the suitable values in the above eqn:

$V_{o} = \frac{120\times 120\times 3\times 1000\times 10^{-6}\times 2.01}{(120 + 120)^{2}}$

$V_{o} = 1.507\ mV$

6 0

3 years ago