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This is problem 5-61 in Serway and Jewett, 4th Ed. (See attached figure).

The problem is to find the force F which will keep the blocks stationary relative to the cart. All surfaces, wheels and pulley are frictionless.

I get

The answer in the back of the book is

Is this right? Here is my work (T is tension in the string):

T - m1*a = 0

m2*g - T = m2*a

Solving for a: a = g*m2/(m1+m2)

The solution in the book must have come from these two equations:

T - m1*a = 0

m2*g - T = 0

which are from the point of view of an observer outside of the cart, I guess.

I realize that if my solution works, the books will also, since it gives a larger F, but will the smaller acceleration not be enough?

Perhaps I don't understand inertial frames very well yet.

Thanks,

Dorothy

The problem is to find the force F which will keep the blocks stationary relative to the cart. All surfaces, wheels and pulley are frictionless.

I get

**F**=(m1+m2+M)(g*m2/(m1+m2)The answer in the back of the book is

**F**=(m1+m2+M)(g*m2/m1)Is this right? Here is my work (T is tension in the string):

T - m1*a = 0

m2*g - T = m2*a

Solving for a: a = g*m2/(m1+m2)

The solution in the book must have come from these two equations:

T - m1*a = 0

m2*g - T = 0

which are from the point of view of an observer outside of the cart, I guess.

I realize that if my solution works, the books will also, since it gives a larger F, but will the smaller acceleration not be enough?

Perhaps I don't understand inertial frames very well yet.

Thanks,

Dorothy