select the correct answer.\nwork is being done in which of these situations? all motions are at a constant…
select the correct answer.\nwork is being done in which of these situations? all motions are at a constant velocity (including velocity = zero).\na. jessica pushes a 25 kilogram cart a distance of 10 meters.\nb. bane carries a 20 kilogram box a distance of 50 meters.\nc. a weightlifter holds a 100 kilogram barbell over his head.\nd. ali is trying to push a truck away from the parking lot.\ne. yana carries a 5 kilogram bag a distance of 1 kilometer.
Answer
Explanation:
Step1: Recall work - formula
Work (W = F\times d\times\cos\theta), where (F) is force, (d) is displacement and (\theta) is the angle between force and displacement. For work to be done, there must be a non - zero displacement in the direction of the force.
Step2: Analyze option A
Jessica pushes a cart. There is a force applied by Jessica and the cart moves in the direction of the applied force. So, work is done. (W = F\times d) (since (\theta = 0^{\circ},\cos\theta= 1)).
Step3: Analyze option B
Bane carries a box. The force he exerts is in the upward direction (to counter - act gravity) and the displacement is in the horizontal direction. So, (\theta = 90^{\circ}) and (\cos\theta = 0), (W=0).
Step4: Analyze option C
The weightlifter holds the barbell. There is no displacement in the direction of the force (the force is upward to counter - act gravity and there is no vertical movement). So, (d = 0) and (W = 0).
Step5: Analyze option D
Ali is trying to push the truck but there is no mention of the truck moving. If there is no displacement, (d = 0) and (W=0).
Step6: Analyze option E
Yana carries a bag. The force she exerts is upward and the displacement is horizontal. So, (\theta = 90^{\circ}), (\cos\theta = 0) and (W = 0).
Answer:
A. Jessica pushes a 25 kilogram cart a distance of 10 meters.