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3 years ago

What is the date of birth for 14

Physics

2 answers:

LUCKY_DIMON [66]3 years ago

8 0

Well from now he or she would have to be born in 2002.

V125BC [204]3 years ago

5 0

- - If you turned 14 this year you would have been born in 2002.
Since this year is 2016 and your 14, then your birthday would be x/x/2002

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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

8. A car travels at a constant velocity of 70 mph for one hour. By the end of the second hour, the car’s velocity was 60 mph. At

Mrac [35]

Answer:

Positive acceleration is in third hour and negative acceleration is in second hour.

Explanation:

Velocity of car in first hour = 70 mph

Velocity of car in second hour = 60 mph

Velocity of car in third hour = 80 mph

Acceleration = Change in velocity / Time

Acceleration in second hour = (60 - 70)/1 = -10 mph²

Acceleration in third hour = (80 - 60)/1 = 20 mph²

So positive acceleration is in third hour and negative acceleration is in second hour.

8 0

3 years ago

A glass falls from a table top and smashes on the floor 0.6 seconds later. How high is the table?

soldi70 [24.7K]

Answer:

1.8 m

Explanation:

Given: Glass falls from a table, smashes 0.6 seconds later

To find: How high a table is

Formula: Vv=gt, dv=1/2gt^2, t=2d/g

Solution: A table's height is measured from the top of the edge down to the floor. The tables are shown both have a height of 30 inches, which is common for many tables.

Data

t = 0.6s

g = 9.81 m/s²

d = ?

Equation

d = $\frac{1}{2}$ $gt$ ²

Math & Units

d = 4.905 (0.6²)
d = 442.676

Hence the table is 1.8 m high

5 0

3 years ago

The temperature of air changes from 0 to 10°C while its velocity changes from zero to a final velocity, and its elevation change

aliya0001 [1]

Answer:

Final velocity = 119.83 m/s

Final elevation = 731.9 m

Explanation:

We are told that temperature of air changes from 0 to 10°C

Thus;

Change in temperature; ΔT = 10 - 0 = 10°C

Also, its velocity changes from zero to a final velocity. Thus;

v1 = 0 m/s

v2 is unknown

Also, its elevation changes from zero to a final elevation.

So, z1 = 0 and z2 is unknown

Now, we want to find v2 and z2 when the internal, kinetic and potential energy are equal.

Thus Equating the formula for both kinetic and internal energy gives;

½m(v2² - v1²) = mc_v•ΔT

m will cancel out and v1 is zero to give;

v2² = 2c_v•ΔT

v2 = √(2c_v•ΔT)

Where c_v is specific heat of constant volume of air with a constant value of 718 J/Kg.K

Thus;

v2 = √(2 × 718 × 10)

v2 = √14360

v2 = 119.83 m/s

To find z2, we will equate potential energy formula to that of the internal energy.

Thus;

mg(z2 - z1) = mc_v•ΔT

m will cancel out and since z1 is zero, then we have;

z2 = (c_v•ΔT)/g

z2 = 718 × 10/9.81

z2 = 731.9 m

4 0

3 years ago

(b)

m_a_m_a [10]

Answer:

Driving force increases, friction forces increase, the driving force is bigger than friction 12.

Explanation:

4 0

3 years ago