Acceleration with force of gravity and friction

AI Thread Summary
To determine the acceleration required for a block to remain stationary on a cart, the static friction force must counteract the gravitational force acting on the block. The relevant equations include F = μ_s * n and F = ma, where n is the normal force equal to mg. An observer on the cart would perceive the block as stationary if the cart accelerates at a rate equal to μ_s * g. The initial confusion stemmed from incorrectly equating forces and acceleration. The final acceleration needed is μ_s / g, which aligns with the principles of Newton's second law.
djokoman95
Messages
7
Reaction score
0

Homework Statement



A block is placed against the vertical front of a cart. The coefficient of static frction between the block and the cart is \mus. What acceleration must the cart have in order that the block does not fall? How would an observer on the cart describe the behavior of the block?

Homework Equations


F=\mus*n
F=ma

The Attempt at a Solution


I have no idea how to start this problem. I know that the force pushing up on the block is equal to mg. I tried drawing acceleration as a horizontal vector, then setting a=mg, then trying to solve, but that didn't quite work out..
 
Physics news on Phys.org
djokoman95 said:
I know that the force pushing up on the block is equal to mg.
Good. What other forces act on the block?
I tried drawing acceleration as a horizontal vector, then setting a=mg, then trying to solve, but that didn't quite work out..
'mg' is a force, which can't be set equal to an acceleration.

Identify all the forces and apply Newton's 2nd law.
 
so after trying a few things, i got\mus /g for my answer. I think that should be right.
 
djokoman95 said:
so after trying a few things, i got\mus /g for my answer. I think that should be right.
Almost. :wink:
 
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

Friction problem of a block sandwiched between 2 surfaces
Replies
6
Views
1K
Newton's law problem: Pushing 2 stacked blocks on a horizontal table
Replies
13
Views
3K
Calculating acceleration of a prism and block connected to a wall through a rope and pulley
Replies
4
Views
382
How friction acts on a block moving down a slope moving side to side
Replies
2
Views
884
How can I determine the instant the block overcomes static friction?
2
Replies
61
Views
3K
Push/Pull Force of wheeled cart on an incline
Replies
7
Views
4K
Coefficient of kinetic friction of a block sliding across the ceiling
Replies
7
Views
1K
Pushing a block against the wall of an elevator that is accelerating
Replies
42
Views
2K
Friction, Mass and Acceleration: Analyzing Block Motion
Replies
6
Views
2K
Two blocks kept side by side and friction between them
Replies
9
Views
2K

Hot Threads

Recent Insights

Back
Top