A weightlifter works out at the gym each day. Part of her routine is to lie on her back and lift a 42 kg barbell straight up from chest height to full arm extension, a distance of 0.48 m.

a. How much work does the weightlifter do to lift the barbell one time?
b. If the weightlifter does 23 repetitions a day, what total energy does she expend on lifting, assuming a typical efficiency for energy use by the body?
c. How many 500 Calorie donuts can she eat a day to supply that energy?

Explanation

A)   Work done for one time = Force x distance

Mass = 42 kg

Acceleration = 9.81 m/s

Distance = 0.48m

B) Work done = Energy

     Total Energy for 23 repetitions will have to do with the total distance covered within that amount of repetition. A full cycle from her chest and back to her chest will have a total distance of  0.48 m multiply by 2 which gives 0.98 m. Therefore for 23 repetition, we have 0.98 m multiply by 23 and this gives 22.08 meter in total.

C)  1 calories is equal to 4.184J

     there 500 calories is equal to 2092 J

   Therefore four (4) of 500 calorie donuts can supply the needed energy of 2092j.

when jerome paddle in flowing river towards east the net speed of jerome will increase

so the net speed of jerome will be given as

now the speed of paul will be same as it is given as he is running on the ground

so

so here we can say since the speed of jerome is more so he will win the race

now as we know the distance so the time difference is given as

so jerome will reach first and the time difference will be 203.55 s or 3.4 min