At an accident scene on a level road, investigators measure a car's skid mark to be 84 m long. It was a rainy day and the coefficient of friction was estimated to be 0.36. Use these data to determine the speed of the car when the driver slammed on (and locked) the brakes. (why does the car's mass not matter?)

Explanation:

Let us assume that v is the final velocity and u is the initial velocity of the car. Let s be the skid marks and $\mu$ be the friction coefficient and m be the mass of car.

Hence, the given data is as follows.

v = 0, s = 84 m, $\mu$ = 0.36

According to Newton's law of second motion the expression for acceleration is as follows.

F = ma

$-\mu N$ = ma

$-\mu mg$ = ma

a = $-\mu g$

Also,

$v^{2} = u^{2} + 2as$

$(0)^{2} = u^{2} + 2(-\mu g)s$

$u^{2} = 2(\mu g)s$

= $\sqrt{2(0.36)(9.81 m/s^{2})(84 m)}$

= 24.36 m/s

Thus, we can conclude that the speed of the car when the driver slammed on (and locked) the brakes is 24.36 m/s.

4 0

3 years ago

radar devices are used by law enforcement to be sure that individuals are driving safely. they tell the officer how fast the veh

coldgirl [10]

The radar device determines the vehicle's instantaneous speed.

I would argue that the purpose of the device is not to determine
whether individuals are driving safely. They only determine whether
individuals are driving within legal speed limits. There's much more
to 'safe' driving than that, but the radar gun can't detect it.

8 0

2 years ago

When thorium (90 protons) ejects a beta particle, the resulting nucleus has

Sav [38]

Answer:

none of the above

Explanation:

The actual answer is '91 protons'. In fact, the beta decay of the thorium-234 is the following:

${}_{90}Th \rightarrow {}_{-1}e+{}_{91}Pa$

where inside the nucleus of Thorium (90 protons), a neutron turns into an electron (the beta particle) + a proton. Therefore, the resulting nucleus (which is Protoactinium) has a total of 90+1 = 91 protons.

So, the correct answer would be '91 protons'.

7 0

2 years ago