Please check my solutions -- Mass being pulled with an angled rope

AI Thread Summary
The discussion focuses on calculating the work done by a force F on a block of mass M, considering friction and normal forces. The force F of 100 N is applied at a 60-degree angle, and the friction force is determined using the formula f = μN, not f = μmg. The normal force N must be calculated correctly, as the applied force's angle affects its vertical component. The correct equation for the normal force includes the downward component of the applied force, leading to N - 100sin(60) = 4 * 9.81. Accurate calculations of these forces are essential for determining the work done.
ZurraMath
Messages
1
Reaction score
0
A block of mass M = 4 kg is pulled by a force F = 100 N forming an angle of 60 degrees with themhorizontal plane with friction coefficient 0.3.

Determine the work of force F, friction force and normal force.

02.png


04.png
 
Physics news on Phys.org
Welcome to PF. :smile:

On your first solution, what are units of "S" for work? What units should Work be in?
 
I assume S to be the displacement?
 
rsk said:
I assume S to be the displacement?
Oh, thanks. I guess the displacement is indeed a variable -- I missed that.
 
The friction force is $$f=\mu N$$ and NOT $$f=\mu mg$$. So to correctly determine the friction force you need to find the normal force N first.
Your equation for the normal force N doesn't seem correct either (though the final result might be correct), it should be $$N-100\sin60=4\cdot 9.81$$ i.e. the force of 100N is actually forming an angle of -60 degrees with the horizontal, that is it is pointing down not up.
 

Thread 'Struggling to understand the concept of this question (ice cube in water optics question)'

TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
View full post »
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 »

Similar threads

Newton's law problem: Pushing 2 stacked blocks on a horizontal table
Replies
13
Views
3K
Pulling a sled across snow with a rope at an angle
Replies
8
Views
4K
Two masses connected by a weighted rope pulled vertically
Replies
5
Views
5K
Solve for the tension in a rope pulling a box
Replies
3
Views
2K
Particle Newtonian Mechanics: Father Pulling 100 lb Sled
Replies
15
Views
2K
How does friction affect the acceleration of a box being pulled by a rope?
Replies
3
Views
2K
Find the mass of a block on an inclined pulley
Replies
3
Views
2K
Webpage title: Optimal Angle for Pulling a Crate with a Friction Rope
Replies
8
Views
4K
A dinner plate, of mass 580 g is pushed .... find work/F
Replies
2
Views
3K
Projectile Motion with Pulley System
Replies
3
Views
2K

Hot Threads

Recent Insights

Back
Top