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Natali5045456 [20]
3 years ago
12

The specific heat of aluminum is 0.0215 cal/g°c. if a 4.55 g sample of aluminum absorbs 2.55 cal of energy, by how much will the

temperature of the sample change?
Physics
1 answer:
lakkis [162]3 years ago
8 0

The formula we will use on this one is:

E = m C ΔT

where,

E = energy

m = mass of sample

C = specific heat

ΔT = change in temperature

 

Calculating for ΔT:

ΔT = E / m C

ΔT = 2.55 cal / (4.55 g * 0.0215 cal/g°C)

ΔT = 0.098 °C

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In the circuit shown, the galvanometer shows zero current. The value of resistance R is :
Tasya [4]

Answer:

its supposed to be (a) 1W

8 0
3 years ago
A lead bar 12 cm long, 2 cm wide, and 2 cm talk has a density of 11.3g/cm3. If you cut the bar in half, what is the density of o
VMariaS [17]

Answer:

The density of one halves  11.3 g / cm cube

Explanation:

Density remain same because cutting the bar in half , mass and volume will decrease to half so density will not change .

density = \frac{mass}{volume}

5 0
3 years ago
A playground merry-go-round has a mass of 50 kg and a diameter of 4.0 m. There are 4 children who want to ride on it. They have
mixer [17]

Answer:

B) I1 = 1680 kg.m^2          I2 = 1120 kg.m^2

C) V = 0.84m/s      T = 29.92s

D) ω2 = 0.315 rad/s

Explanation:

The moment of inertia when they are standing on the edge:

I1 = 1/2*M*R^2 + (m1+m2+m3+m4)*R^2   where M is the mass of the merry-go-round.

I1 = 1680 kg.m^2

The moment of inertia when they are standing half way to the center:

I2 = 1/2*M*R^2 + (m1+m2+m3+m4)*(R/2)^2

I2 = 1120 kg.m^2

The tangencial velocity is given by:

V = ω1*R = 0.84m/s

Period of rotation:

T = 2π / ω1 = 29.92s

Assuming that there is no friction and their parents are not pushing anymore, we can use conservation of the angular momentum to calculate the new angular velocity:

I1*ω1 = I2*ω2    Solving for ω2:

ω2 = I1*ω1 / I2 = 0.315 rad/s

5 0
3 years ago
Attempt 2 You have been called to testify as an expert witness in a trial involving a head-on collision. Car A weighs 15151515 l
Natasha_Volkova [10]

Answer:

v = 28.98 ft / s

Explanation:

For this problem we must solve it in parts, let's start by looking for the speed of the two cars after the collision

In the exercise they indicate the weight of each car

          Wₐ = 1500 lb

          W_b = 1125 lb

Car B's velocity from v_b = 42.0 mph westward, car A travels east

let's find the mass of the vehicles

             W = mg

             m = W / g

             mₐ = Wₐ / g

             m_b = W_b / g

             mₐ = 1500/32 = 46.875 slug

             m_b = 125/32 = 35,156 slug

Let's reduce to the english system

             v_b = 42.0 mph (5280 foot / 1 mile) (1h / 3600s) = 61.6 ft / s

We define a system formed by the two vehicles, so that the forces during the crash have been internal and the moment is preserved

we assume the direction to the east (right) positive

initial instant. Before the crash

           p₀ = mₐ v₀ₐ - m_b v_{ob}

final instant. Right after the crash

           p_f = (mₐ + m_b) v

the moment is preserved

           p₀ = p_f

           mₐ v₀ₐ - m_b v_{ob} = (mₐ + m_b) v

           v = \frac{ m_a \ v_{oa} - m_b \ v_{ob}  }{ m_a +m_b}

we substitute the values

           v = \frac{ 46.875}{82.03} \ v_{oa} -  \frac{35.156}{82.03} \ 61.6

           v = 0.559 v₀ₐ - 26.40                  (1)

Now as the two vehicles united we can use the relationship between work and kinetic energy

the total mass is

              M = mₐ + m_b

              M = 46,875 + 35,156 = 82,031 slug

starting point. Jsto after the crash

              K₀ = ½ M v²

final point. When they stop

             K_f = 0

The work is

             W = - fr x

the negative sign is because the friction forces are always opposite to the displacement

Let's write Newton's second law

Axis y

           N-W = 0

           N = W

the friction force has the expression

            fr = μ N

we substitute

            -μ W x = Kf - Ko

             

            -μ W x = 0 - ½ (W / g) v²

            v² = 2 μ g x  

            v = \sqrt{ 2 \ 0.750 \ 32 \ 17.5}Ra (2 0.750 32 17.5  

            v = 28.98 ft / s

3 0
2 years ago
Assume this is an acceleration graph, where the X axis represents time in seconds and the Y axis represent velocity in m/s. Whic
Vilka [71]

Answer:

D) Acceleration is positive and increasing.

Explanation:

Acceleration is defined as the rate of change of velocity per unit time; in formulas:

a=\frac{\Delta v}{\Delta t}

where \Delta v is the variation of velocity and \Delta t is the variation in time.

The graph shows the velocity vs the time of a moving object. We can see that \Delta v is the increment on the y-axis, while \Delta t is the increment on the x axis: therefore, the ratio \frac{\Delta v}{\Delta t} is the slope of the curve. In fact, in a velocity-time graph, the slope of the curve corresponds to the acceleration of the object.

In this particular graph, we see that the slope of the curve continues to increase: therefore, the acceleration is positive (because the slope is positive, since the velocity is increasing) and increasing (because the slope is increasing).

3 0
3 years ago
Read 2 more answers
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