Physics, 16.10.2020 01:01 Blakemiller2020

How can you predict the number of swings an 80 cm pendulum will make in 15 seconds?

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The period of the pendulum is equal to the square root (0.8 / 9.8). That is the time for one oscillation T. You then divide 15/T to find number of swings in 15 seconds.

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

If the heat engine is a perfect carnot cycle engine, thenefficiency = (t2-t1)/t2 where t1=temperature of cold reservoir ( ° k) = 135 t2=temperature of hot reservoir ( ° k) = 325thereforeefficiency = (t2-t1)/t2 = (325-135)/325 = 0.5846 = 58% note: this is the theoretical maximum efficiency of a perfect heat engine. real-life engines do not achieve this value.

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