How much work does a supermarket checkout attendant do on a can of soup he pushes 0.600 m horizontally with a force of 5.00 N? Express your answer in joules and kilocalories.
Solution:
The work W that a force F does on an object is the product of the magnitude F of the force, times the magnitude d of the displacement, times the cosine of the angle θ between them. In symbols,
W=Fdcosθ
We are given the following values: F=5.00 N, d=0.600 m, and θ=0∘.
Substitute the given values in the formula for work.
WWWW=Fdcosθ=(5.00 N)(0.600 m)cos0∘=3.00 Nm=3.00 J (Answer)
The work done is 3.00 Joules. Now, we can convert this in unit of kilocalories knowing that 1 kcal=4186 J.
WWWW=3.00 J=3.00 J × 4186 J1 kcal=0.000717 kcal=7.17×10−4 kcal (Answer)
The work done in kilocalories is about 7.17×10−4.