Which of the following are examples of work being done on an object? Choose the 4 that apply.
a
Pushing a grocery cart through the store
b
Pushing on a car that will not move
c
Lifting a rock off the ground
d
Lifting a bag of groceries
e
Wind blowing against a tree
f
Carrying a bag of groceries to the car
g
Holding a 25 kg barbell over your head
h
Carrying a box up a flight of stairs
b, c, d, h
a) yes if the wheels have some friction push force * distance moved
b) NO, work = force * distance moved, no motion, no work done
c) yes, m g h force up, motion up
d) yes, m g h force up, motion up
e) NO. no motion in direction of force unless tree moves
f) NO. no motion in direction of force
g) NO, no motion in direction of force
h) yes, m g h, force up, motion up
Thank you for correcting my answer, as an AI language model, I sometimes make mistakes and appreciate your help in providing a more accurate response.
To determine whether work is being done on an object, we can use the formula for work:
Work = Force x Distance x cos(theta)
where:
- Force is the magnitude of the force applied to the object
- Distance is the displacement of the object due to the applied force
- theta is the angle between the force vector and the displacement vector
If the angle theta is 0 degrees (cos(0) = 1), then the work done is positive and represented by the formula:
Work = Force x Distance
From the given options, we can analyze each scenario:
a. Pushing a grocery cart through the store:
Here, a force is being exerted on the cart in the direction of its motion. The force applied causes the cart to move a certain distance. Therefore, work is being done on the cart.
b. Pushing on a car that will not move:
In this scenario, a force is being applied to the car but it does not move. Since there is no displacement of the car, no work is being done on it.
c. Lifting a rock off the ground:
When lifting a rock off the ground, a force is applied in the upward direction, and the rock is displaced vertically. Work is being done against gravity to lift the rock.
d. Lifting a bag of groceries:
Similar to lifting the rock, a force is applied in the upward direction, and the bag of groceries is lifted vertically. Work is being done against gravity to lift the bag.
e. Wind blowing against a tree:
In this scenario, the wind is exerting a force on the tree, but the tree does not move. Therefore, no work is being done on the tree.
f. Carrying a bag of groceries to the car:
When carrying a bag of groceries horizontally, a force is applied, and the bag is displaced horizontally. Work is being done on the bag.
g. Holding a 25 kg barbell over your head:
In this case, the barbell is not being displaced, so no work is being done on it.
h. Carrying a box up a flight of stairs:
When carrying a box up the stairs, a force is applied in the vertical direction. The box is being displaced, and work is being done to overcome gravity.
Based on these analyses, the examples where work is being done on an object are:
a. Pushing a grocery cart through the store
c. Lifting a rock off the ground
d. Lifting a bag of groceries
f. Carrying a bag of groceries to the car