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3 years ago

6

A child pushes a toy box across the floor in 5 seconds. If he did 30 J of work on the toy box, what amount of power was required

to complete this action?
6 watts
25 watts
150 watts
35 watts

2 answers:

weqwewe [10]3 years ago

8 0

6 WATTS, WNJOY MY FRIEND

s2008m [1.1K]3 years ago

4 0

My answer is 6 watts because 30J/5s is 6

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You place an ice cube of mass 7.50×10−3kg and temperature 0.00∘C on top of a copper cube of mass 0.540 kg. All of the ice melts,

lbvjy [14]

Answer:

The value is $T_c = 12 .1 ^oC$

Explanation:

From the question we are told that

The mass of the ice cube is $m_i = 7.50 *10^{-3} \ kg$

The temperature of the ice cube is $T_i = 0^o C$

The mass of the copper cube is $m_c = 0.540 \ kg$

The final temperature of both substance is $T_f = 0^oC$

Generally form the law of thermal energy conservation,

The heat lost by the copper cube = heat gained by the ice cube

Generally the heat lost by the copper cube is mathematically represented as

$Q = m_c * c_c * [T_c - T_f ]$

The specific heat of copper is $c_c = 385J/kg \cdot ^oC$

Generally the heat gained by the ice cube is mathematically represented as

$Q_1 = m_i * L$

Here L is the latent heat of fusion of the ice with value $L = 3.34 * 10^{5} J/kg$

So

$Q_1 = 7.50 *10^{-3} * 3.34 * 10^{5}$

=> $Q_1 = 2505 \ J$

So

$2505 = 0.540 * 385 * [T_c - 0 ]$

=> $T_c = 12 .1 ^oC$

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2 years ago

A ball is thrown vertically upward from the top of a building 112 feet tall with an initial velocity of 96 feet per second. The

nordsb [41]

Answer:

$t=6.96s$

Explanation:

From this exercise, our knowable variables are <u>hight and initial velocity </u>

$v_{oy}=96ft/s$

$y_{o}=112ft$

To find how much time does the <u>ball strike the ground</u>, we need to know that the final position of the ball is y=0ft

$y=y_{o}+v_{oy}t+\frac{1}{2}gt^{2}$

$0=112ft+(96ft/s)t-\frac{1}{2}(32.2ft/s^{2})t^{2}$

Solving for t using quadratic formula

$t=\frac{-b±\sqrt{b^{2}-4ac } }{2a}$

$a=-\frac{1}{2} (32.2)\\b=96\\c=112$

$t=-0.999s$ or $t=6.96s$

<u><em>Since time can't be negative the answer is t=6.96s</em></u>

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3 years ago

A spring stretches 0.2 cm per newton of applied force. An object is suspended from the spring and a deflection of 3 cm is observ

siniylev [52]

Answer:

$m=1.53kg$

Explanation:

To solve this problem we use the Hooke's Law:

$F=k*\Delta x$ (1)

F is the Force needed to expand or compress the spring by a distance Δx.

The spring stretches 0.2cm per Newton, in other words:

1N=k*0.2cm ⇒ k=1N/0.2cm=5N/cm

The force applied is due to the weight

$F=mg$

We replace in (1):

$mg=k*\Delta x$

We solve the equation for m:

$m=k*\Delta x/g=5*3/9.81=1.53kg$

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3 years ago

A 2.0-kg block is on a perfectly smooth ramp that makes an angle of 30° with the horizontal. (a) What is the block’s acceleratio

lukranit [14]

Answer:

The forces that do non-zero work on the block are gravity and normal reaction force

Explanation:

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3 years ago

You are an engineer in charge of designing a new generation of elevators for a prospective upgrade to the Empire State Building.

DanielleElmas [232]

Answer:

t_total = 23.757 s

Explanation:

This is a kinematics exercise.

Let's start by calculating the distance and has to reach the limit speed of

v = 18.8 m / s

v = v₀ + a t₁

the elevator starts with zero speed

v = a t₁

t₁ = v / a

t₁ = 18.8 / 2.40

t₁ = 7.833 s

in this time he runs

y₁ = v₀ t₁ + ½ a t₁²

y₁ = ½ a t₁²

y₁ = ½ 2.40 7.833²

y₁ = 73.627 m

This is the time and distance traveled until reaching the maximum speed, which will be constant throughout the rest of the trip.

x_total = x₁ + x₂

x₂ = x_total - x₁

x₂ = 373 - 73,627

x₂ = 299.373 m

this distance travels at constant speed,

v = x₂ / t₂

t₂ = x₂ / v

t₂ = 299.373 / 18.8

t₂ = 15.92 s

therefore the total travel time is

t_total = t₁ + t₂

t_total = 7.833 + 15.92

t_total = 23.757 s

6 0

3 years ago