Aperson measures her heart rate by counting the number of beats in 30 s. if 36 ± 2 beats are counted in 30.0 ± 0.4 s, what is the heart rate and its uncertainty in beats per minute?

For the heart rate :

n = number of heat beats = 36

t = time taken to measure = 30 s = 30/60 min = 0.5 min            (since 1 min = 60 sec)

R = heart rate

Heart rate is given as

inserting the values

R = 72 min⁻¹

For uncertainty :

Δn = uncertainty in number of heat beats = ± 2

Δt = uncertainty in time taken = ± 0.4 s = ± 0.4/60 min = ± 0.0067 min            (since 1 min = 60 sec)

ΔR = uncertainty in heart rate

uncertainty in Heart rate is given as

inserting the values

ΔR = ± 4.96 min⁻¹

the motion of a pendulum is a classic example of mechanical energy conservation. a pendulum consists of a mass (known as a bob ) attached by a string to a pivot point. as the pendulum moves it sweeps out a circular arc, moving back and forth in a periodic fashion.

because if the tool that you are using is not balanced it there would be false mass.