Physics, 18.01.2020 03:31 jasminethomas383

Alarge fake cookie sliding on a horizontal surface is attached to one end of a horizontal spring with spring constant k = 375 n/m; the other end of the spring is fixed in place. the cookie has a kinetic energy of 20.0 j as it passes through the position where the spring is unstretched. as the cookie slides, a frictional force of magnitude 10.0 n acts on it.

(a) how far will the cookie slide from the position where the spring is unstretched before coming momentarily to rest?
m

(b) what will be the kinetic energy of the cookie as it slides back through the position where the spring is unstretched?
j(a) how far will the cookie slide from the position where the spring is unstretched before coming momentarily to rest?
m

(b) what will be the kinetic energy of the cookie as it slides back through the position where the spring is unstretched?
j

Answers: 3

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Answer from: liyahguyton

a) $x=0.301\ m$

b) $KE=26.338\ J$

Explanation:

Given:

spring constant, $k=375\ N.m^{-1}$ kinetic energy of cookie, $KE=20\ J$ frictional force on the cookie, $f=10\ N$

Now the kinetic energy here is changing into frictional energy and the spring potential energy.

So, by the law of energy conservation:

$KE=\rm spring\ potential\ energy+frictional\ loss$

$KE=\frac{1}{2} k.x^2+f.x$

where:

distance travelled by the cookie from the unstretched position to the stretched position of the spring.

$20=\frac{1}{2} \times 375\times x^2+10\times x$

$375\times x^2+20\times x-40=0$

$x=0.301\ m$ ( neglecting the negative value)

Now, after the compression of the spring there is no kinetic energy for the moment as the velocity of the cookie is zero but there is a spring potential energy due to the compressed spring.

So, here we have the spring potential energy getting converted into kinetic energy and the frictional losses:

U=KE+E_f

where:

U = spring potential energy

KE = kinetic energy

E_f= energy lost due to friction

$\frac{1}{2} \times 375\times 0.301=KE+10\times 0.301$

$KE=26.338\ J$

Answer from: Quest

answer: the correct answer is 1.

explanation: there are various process in which a radioactive nuclei decays:

1) alpha decay: in this process, a heavier nuclei decays into lighter nuclei by releasing alpha particle. the mass number is reduced by 4 units.

$_a^z\textrm{x}\rightarrow _{a-2}^{z-4}+_2^4\alpha$

2) electron capture: in this decay process, a parent nuclei absorbs an electron and gets converted into a neutron. simply, a proton and an electron combines together to form a neutron. mass number does not change in this process.

$_a^z\textrm{x}+_{-1}^0\textrm{e}\rightarrow _{z-1}^a\textrm{y}$

3) gamma ray emission: it is a decay process in which an unstable nuclei gives excess energy by a spontaneous electromagnetic process. this decay releases $\gamma -radiations$ . this process does not change the mass number.

$_a^z\textrm{x}^*\rightarrow _a^z\textrm{x}+_0^0\gamma$

4) positron emission: it is a type of decay process, in which a proton gets converted to neutron and an electron neutrino. this is also known as $\beta ^+$ -decay. in this the mass number remains same.

$_a^z\textrm{x}\rightarrow _{z-1}^a\textrm{y}+_{+1}^0e$

from the above information, we see that only alpha-decay is producing a change in the mass number of the nucleus.

Answer from: Quest

this could be newton#'s law of cooling. the cooling curve is exponential

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