Calculating Work on Incline: Solving for Gravitational Force Work

AI Thread Summary
The discussion revolves around calculating the work done by gravitational force on a box being pushed up a frictionless incline. The user initially uses the formula Wg = mgh and calculates the height using the sine of the incline angle, resulting in a work value of 358.1 J. However, they realize that the work done by gravity should be considered negative since it opposes the direction of movement. The clarification leads to the understanding that gravitational work is stored as potential energy, confirming that the correct approach involves recognizing the sign of the work done by gravity. The final takeaway emphasizes the importance of considering the direction of forces when calculating work in physics problems.
mrnastytime
Messages
28
Reaction score
0

Homework Statement


A horizontal force of magnitude F = 197 N is used to push a box of mass m = 5 kg from rest a distance d = 13 m up a frictionless incline with a slope q = 34°.


Homework Equations


How much work is done on the box by the gravitational force during this same displacement?


The Attempt at a Solution


Wg=mgh
Wg=5*9.81*7.3
i got 7.3 by using sin34=h/13
Wg=358.1 J
The answer i got is wrong according to the online hw. What am i missing? did i use the wrong formula?
 
Physics news on Phys.org
Maybe it would be negative?

Work by you is +, work by gravity is stored as potential = (-)?
 
wow, it is negative. thank you very much!
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »

Thread 'Egg Drop Challenge! Need ideas for winning designs'

I was thinking using 2 purple mattress samples, and taping them together, I do want other ideas though, the main guidelines are; Must have a volume LESS than 1600 cubic centimeters, and CAN'T exceed 25 cm in ANY direction. Must be LESS than 1 kg. NO parachutes. NO glue or Tape can touch the egg. MUST be able to take egg out in less than 1 minute. Grade A large eggs will be used.
View full post »

Similar threads

Physics — Net work on a box being pulled…
Replies
6
Views
2K
Need help on a work problem -- Pushing a shoe box up a ramp
Replies
8
Views
2K
Work Done by Friction & Gravity on Incline: Explained
Replies
7
Views
7K
Work problem, box moves at h=.25 with F=85N
Replies
4
Views
1K
Work energy theorem problem -- Block sliding up a curved incline
Replies
10
Views
1K
Difficulty in deciding when to apply work energy theorem
Replies
2
Views
1K
Solving Incline Problem with Normal Force: 39.36
Replies
13
Views
2K
Work done by gravitational force (new problem)
Replies
9
Views
2K
Calculate the work done moving a crate
Replies
3
Views
3K
Solving Work & Forces Problems: Alpine Rescue Team
Replies
1
Views
2K

Hot Threads

Recent Insights

Back
Top