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3 years ago

Two objects made of the same material are heated to 60 oC and 90 oC. According to

Physics

2 answers:

earnstyle [38]3 years ago

6 0

Answer:

The newton law of cooling is:

dQ/dt = -h*a(To - Ta)

Where h and a are constants, To is the temperature of the object and Ta is the temperature of the ambient.

this means that initially if in both cases Ta is the same, the object with higher temperature cools faster.

Now, obviously, if we want to know which object cools faster to a given temperature, for example, 30°C, the object with 60°C will reach that temperature in less time than the other one. (this is because the hot object cools faster at the beginning, but as it starts to lose temperature, the rate at which it colls starts to decrease)

nlexa [21]3 years ago

4 0

Assuming that there is in a vacuum, the two object will cool at the same rate, because the objects are made of the same material they will have the same cooling rate, assuming the surrounding temperature is the same.

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3 years ago

You throw a bouncy rubber ball and a wet lump of clay, both of mass m, at a wall. Both strike the wall at speed v, but while the

lana [24]

Answer:

<em>The fifth option is the correct answer: mv; 2 mv</em>

Explanation:

<u>Change of Momentum</u>

Assume an object has a momentum p1 and after some interaction it now has a momentum p2, the change of momentum is

$\Delta p=p_2-p_1$

The momentum is computed as

$p=mv$

Where m is the mass of the object and v its speed. Now let's analyze the situation of both the ball and the clay.

The clay has an initial speed v and a mass m, thus its initial momentum is

$p_1=mv$

When it hits the wall, it sticks, thus its final speed is 0 and

$p_2=0$

The change of momentum is

$\Delta p=0-mv=-mv$

The absolute change is mv

Now for the ball, the initial condition is the same as it was for the clay, but the ball hits back at the same speed, thus its final momentum is

$p_2=-mv$

The change of momentum is

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3 0

3 years ago

To win the game, a placekicker must kick a football from a point 44 m (48.1184 yd) from the goal, and the ball must clear the cr

Ganezh [65]

Answer:

The distance by the ball clear the crossbar is 1.15 m

Explanation:

Given that,

Distance = 44 m

Speed = 24 m/s

Angle = 31°

Height = 3.05 m

We need to calculate the horizontal velocity

Using formula of horizontal velocity

$u_{x}=u\cos\theta$

Put the value into the formula

$u_{x}=24\cos(31)$

$u_{x}=20.5\ m/s$

We need to calculate the vertical velocity

Using formula of vertical velocity

$u_{y}=u\sin\theta$

Put the value into the formula

$u_{y}=24\sin(31)$

$u_{y}=12.3\ m/s$

We need to calculate the time

Using formula of time

$t=\dfrac{d}{u_{x}}$

Put the value into the formula

$t=\dfrac{44}{20.5}$

$t=2.1\ sec$

We need to calculate the vertical height

Using equation of motion

$h=u_{y}t+\dfrac{1}{2}at^2$

Put the value into the formula

$h=12.3\times2.1-\dfrac{1}{2}\times9.8\times(2.1)^2$

$h=4.2\ m$

We need to calculate the distance by the ball clear the crossbar

Using formula for vertical distance

$d=h-3.05$

Put the value of h

$d=4.2-3.05$

$d=1.15\ m$

Hence, The distance by the ball clear the crossbar is 1.15 m

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3 years ago

If Bert the Bat travels East at 200 meters in 10 seconds, what is his velocity?

dexar [7]

Answer:

20m/s due east

Explanation:

Given parameters:

Displacement eastward = 200m

Time = 10s

Unknown:

Velocity = ?

Solution:

Velocity is the displacement divided by time;

Velocity = $\frac{displacement}{time}$

Velocity = $\frac{200}{10}$ = 20m/s due east

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3 years ago