1. how much work do you do on a 25-kg backpack when you walk a horizontal distance of 100 m?

-I got 2,500 J

4. if you friend pushes a lawnmower four times as far as you do while exerting only half the force, which one of you does more work? how much more? ( I don't understand this question)

7.why does one get tired when pushing against a stationary wall when no work is done on the wall?
-I got because the wall is pushing back with the same equal amount of force.

9. which requires more work streching a strong spring a certain distance or streching a weak spring the same distace? Why?

1. The answer is zero, because your motion is perpendicular to that of the weight force. Npte that you must also multiply M by g to get weight, but the answer is still zero.

4. What don't you understand? Work is force times distance. If your friend uses half the force but goes four times as far, how much greater is his work done than yours? The relative work done (His work)/(Your work) = 4 x (1/2) = ?

7. Caloriees must be burned to keep muscles in a state of tension, even when they are not in motion.

9. What do you think? Remember the definition of work. The work done stretching a spring is
(1/2)*(distance) * (maximum force)
The weaker spring requires a lower maximum force to stretch the same distance as the stronger spring.

4. In this scenario, your friend pushes the lawnmower four times as far as you do, but exerts only half the force. To determine who does more work, we can use the formula:

Work = Force × Distance

Let's assume you exert a force of F and push the lawnmower a distance of D. Therefore, your friend exerts a force of 0.5F and pushes the lawnmower for a distance of 4D.

The work you do is:
Work = F × D

The work your friend does is:
Work = (0.5F) × (4D) = 2F × D = 2 times the work you do.

So, your friend does more work, and the amount of extra work is twice the work you do.

7. When pushing against a stationary wall, no work is done on the wall because the wall does not move. However, you may still feel tired because your muscles are working and exerting force against the wall. Even though no work is done on the wall, your muscles consume energy, and prolonged muscle contraction can lead to fatigue.

9. To determine which requires more work, let's consider the formula:

Work = Force × Distance

Assuming both springs have the same distance for stretching, let's say D. The work required to stretch the strong spring can be represented as Work1 = F1 × D, where F1 is the force required to stretch the strong spring. Similarly, the work required to stretch the weak spring can be represented as Work2 = F2 × D, where F2 is the force required to stretch the weak spring.

Since both springs are stretched the same distance, the force required to stretch the strong spring, F1, would generally be greater than the force required to stretch the weak spring, F2. Therefore, the strong spring would require more work, as the force needed is greater.

1. To find the amount of work done on a backpack, you can use the formula W = F × d, where W is the work, F is the force applied, and d is the distance traveled. In this scenario, the force applied is the weight of the backpack, which can be calculated using the formula F = m × g, where m is the mass and g is the acceleration due to gravity. Plugging in the given values, you have F = 25 kg × 9.8 m/s² = 245 N. Now you can calculate the work done using the formula W = 245 N × 100 m = 24,500 J. So the correct answer is 24,500 J, not 2,500 J as you mentioned.

4. This question is asking about the comparison of work done by you and your friend while pushing lawnmowers. Let's assume you exert a force of 10 N and push the lawnmower 2 meters, while your friend exerts a force of 5 N and pushes the lawnmower 8 meters. Work is calculated using the formula W = F × d. So, for your work, W1 = 10 N × 2 m = 20 J. And for your friend's work, W2 = 5 N × 8 m = 40 J. Your friend does more work (40 J) compared to you (20 J) because they exerted a smaller force over a greater distance.

7. When you push against a stationary wall and feel tired, it is because you are continuously applying force against an immovable object. Although no work is done on the wall because it does not move, your muscles are still exerting effort to push with the same amount of force repeatedly. This sustained muscular activity leads to fatigue over time, even if no external work is accomplished.

9. The amount of work required to stretch a spring depends on its stiffness (or spring constant) and the distance it is stretched. Generally, a strong spring will have a higher spring constant compared to a weak spring. When you stretch a spring, the work done is calculated using the formula W = 0.5 × k × (d² - d₀²), where W is the work, k is the spring constant, d is the final distance, and d₀ is the initial distance. Since a strong spring has a higher spring constant, it will require more work to stretch it the same distance compared to a weak spring with a lower spring constant.