force needed to move 42.5 kg fridge 5 m; static friction is

[alice]

im uncertain with this question. It's a physics question.

You are required to drag a fridge from one side of the garage to the other, a distance of 5 meters. The fridge weighs 42.5 kg, and in addition, a cartoon of beer (30 x 375 ml cans) has been left in the fridge. The coefficient of static friction between the fridge and the floor is 0.78 and the coefficient of dynamic friction between the fridge and the floor is 0.67. How much force must you exert to start the fridge in motion and how much force is required to keep the fridge in motion? You now decide to return the fridge to its original position but decide to place a slide under the fridge to lessen the friction. The slide reduces the coefficient of dynamic friction between the fridge and the floor to 0.39. What was the percentage reduction in the force required to keep the fridge in motion using the slide compared to no slide?

Regards
Alice

 

[wjm11]

Re: Puzzled on friction

You are required to drag a fridge from one side of the garage to the other, a distance of 5 meters. The fridge weighs 42.5 kg, and in addition, a cartoon of beer (30 x 375 ml cans) has been left in the fridge. The coefficient of static friction between the fridge and the floor is 0.78 and the coefficient of dynamic friction between the fridge and the floor is 0.67. How much force must you exert to start the fridge in motion and how much force is required to keep the fridge in motion? You now decide to return the fridge to its original position but decide to place a slide under the fridge to lessen the friction. The slide reduces the coefficient of dynamic friction between the fridge and the floor to 0.39. What was the percentage reduction in the force required to keep the fridge in motion using the slide compared to no slide?

Friction always acts in the direction opposite that of motion. The force due to friction is simply the Normal Force, N, times the coefficient of friction, mu,

F = (mu)(N)

On a level surface, N is equal and opposite to the weight, W, of the object. Weight is equal to mass times acceleration due to gravity,

W = mg

Combining these, we have

F = mu(mg)

Use the coefficient of static friction to calculate force required to start the fridge moving. Use the coefficient of kinetic friction to find force required to keep it moving.

The distance has nothing to do with finding the force. The distance would be used to calculate the amount of work done: Work = Force x Distance.

Hope that helps.

 

[alice]

Re: Puzzled on friction

do i need to find out the density that the beer contains or anything like that??
i am still unsure with the question for some reason though

Alice

 

[Deleted member 4993]

Re: Puzzled on friction

do i need to find out the density that the beer contains or anything like that??
i am still unsure with the question for some reason though

Alice

As I see the problem - you need to know the weight of the carton of beer in the fridge. That plus the weight of the fridge will make the normal force - responsible for friction.

 

[alice]

Re: Puzzled on friction

just off hand, would you no the rule i oculd use to find that? or is it simply just 30*350?

 

[wjm11]

Re: Puzzled on friction

do i need to find out the density that the beer contains or anything like that??

We only know the mass of the fridge to half a kg, so I think it’s reasonable to approximate the density of beer to be the same as water: 1 gm/cc or 1 gm/ml

Mass = Density x Volume

You take it from there.

 

[alice]

Re: Puzzled on friction

Thanks guys
Really appreciate all of your help!!! use are the best

Cheers
Alice