Question

You overindulged on a delicious dessert, so you plan to work off the extra calories at the gym. To accomplish this, you decide to do a series of arm raises holding a 5.5kg weight in one hand. The distance from your elbow to the weight is 38cm , and in each arm raise you start with your arm horizontal and pivot it until it is vertical. Assume that the weight of your arm is small enough compared with the weight you are lifting that you can ignore it. As is typical, your muscles are 20{\rm \\%} in converting the food energy they use up into mechanical energy, with the rest going into heat.If your dessert contained 370 food calories, how many arm raises must you do to work off these calories?Express your answer using two significant figures.Is it realistic to do them all in one session? Y or N

Answer 1

Answer:

$N = 15 times$

Yes it is realistic

Explanation:

Each time the energy that is used to raise the mass is given as

$U = mgh$

here we know that

m = mass of the object = 5.5 kg

h = height = 38 cm

now we have

$U = mgh$

$U = (5.5)(9.81)(0.38)$

$U = 20.5 J$

now each time when mass is raised only 20% food energy is converted into work done to raise the mass

so total burn calorie in each lift of the mass is given as

$20.5 = 0.20E$

$E = 102.5 J$

now we know that total food energy that is needed to burn is given as

$U = 370 calorie$

$U = 1548 J$

so total number of lifts required is given as

$N = \frac{1548}{102.5}$

$N = 15 times$

Yes it is realistic