Physics, 17.01.2020 01:31 princess5964

The driver of a car traveling at 17.7 m/s ap-
plies the brakes and undergoes a constant
deceleration of 1.38 m/s.
how many revolutions does each tire make
before the car comes to a stop, assuming that
the car does not skid and that the tires have
radii of 0.42 m?
answer in units of rev.

Answers: 2

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Answer from: dajahp

43 revolutions.

Explanation:

The time it takes for the car to stop is

$t=v_i/a=\frac{17.7m/s}{1.38m/s^2}=12.83s$

The distance it travels in that time is

$d=\frac{1}{2}at^2=\frac{1}{2}(1.38)(12.83) ^2=113.5m$

The number of revolutions that the tires make is then

$n=\frac{d}{2\pi r} =\frac{113.5}{2\pi *0.42} =\boxed{43\:revolutions}$

The last calculation just asks the question "how many tire circumferences fit into d=113 meters?"

Answer from: Quest

force is based upon mass and acceleration.the statement is not always true.

it can be explained from newton's second law of motion.

as per newton's second law of motion the rate of change of momentum is directly proportional to the applied force and takes place along the direction of force.

mathematically it can be written as -

$f\alpha \frac{dp}{dt}$

⇒ $f= k \frac{dp}{dt}$

here k is the proportionality constant whose value is 1.

$f=\frac{dp}{dt}$

$f= \frac{d[mv]}{dt}$

$f= m\frac{dv}{dt} +v\frac{dm}{dt}$

$f=ma+v\frac{dm}{dt}$ [a is the acceleration=dv/dt]

hence we see that force not only depends on mass and acceleration but also on velocity and rate of change of mass. force f will depend on mass and acceleration only when mass is constant.

hence the statement that force is based upon mass and acceleration is false.

Answer from: Quest

the design of a ski jumping suit involves a trade-off between giving the skiers lift to get higher jumps and ensuring the skier does not face a lot of drag before the jump itself. an expansive suit may to lift the skier higher, but at the same time, it will also increase the air resistance. higher air resistance as the skier goes down the slope limits the speed of the jump. a big suit also increases the risk of losing balance or control, especially if there's a strong gust of wind. while technologically enhanced suits a lot, clothing is not the only factor in a ski jumper’s success. gathering speed while skiing down the slope, ensuring good speed on the ramp, and maintaining good body posture and form in the air all contribute to a ski jumper's success.

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The driver of a car traveling at 17.7 m/s ap-
plies the brakes and undergoes a constant
...

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