I'm having a problem understanding a question. "If a man exerts a 200N force while pushing a crate 5.0 m across a floor against a frictional resistance of 40N, how much energy was expended by the person pushing?" I can figure out work done on the box and those sorts of questions but I don't get what is meant by how much energy is the man expending.
The work expended is the applied force (200 N) times the distance the crate moved (5.0 m). The amount of friction does not affect that result.
Thank you.
In this context, "how much energy was expended by the person pushing" refers to the amount of work done by the person in overcoming the frictional resistance and pushing the crate. Energy and work are closely related concepts.
To calculate the energy expended by the person pushing, you can use the formula:
Energy (work) = Force × Distance
In this case, the force exerted by the person pushing the crate is 200 N and the distance moved against the frictional resistance is 5.0 m. However, since the frictional resistance opposes the motion of the crate, the work done against the friction needs to be subtracted from the total work done.
The frictional force is given as 40 N and the displacement is also 5.0 m. So the work done against friction is:
Work against friction = Force of friction × Distance = 40 N × 5.0 m = 200 J
Substituting the values into the formula, the total work done by the person pushing the crate can be calculated as:
Total work done = Force × Distance - Work against friction
= (200 N × 5.0 m) - 200 J
= 1000 J - 200 J
= 800 J
Therefore, the amount of energy expended by the person pushing the crate is 800 Joules (J).
To understand how much energy is being expended by the person pushing the crate, we need to refer to the concept of work. In physics, work is defined as the transfer of energy through the application of force over a distance.
In this context, when the man exerts a force of 200N to push the crate, he is performing work against the frictional resistance. The work done can be calculated by multiplying the force applied by the distance over which the force is applied.
The equation for work is:
Work = Force x Distance
In this case, the force exerted by the man is 200N, and the distance over which the force is applied is 5.0m. Therefore:
Work = 200N x 5.0m = 1000 Joules
So, the work done by the man pushing the crate is 1000 Joules. Since work is defined as the transfer of energy, the amount of energy expended by the person pushing the crate is also 1000 Joules.