I got a take home test for AP Physics B and I've completed it. I just wanted to check with some people to see if they agree with some of the questions I had some difficulty with. I'll list the questions & how I thought they are solved. Any and all feedback is greatly appreciated- thanks for the help!(adsbygoogle = window.adsbygoogle || []).push({});

8. A student pulls a box of books on a smooth horizontal floor with a force of 100 N in a direction of 37 degrees above the horizontal. If the mass of the box and hte books is 40.0 kg, what is the acceleration of the box?

A) 0 m/s^2 B) 1.5 m/s^2 C) 1.9 m/s^2 D) 2.0 m/s^2 E) 3.3 m/s^2

I chose answer e- Sigma F(sub x)= F(sub t)- F(sub g in the x plane)= m (a)

I resolved F(sub g) into the x component 392*sin(37)=235.911 and plugged into the equation. I solved for a by doing 235.911 + 40(a) = 100. It didn't come out to exactly 3.3, but I figured with sig figs and what not it was the best choice.

13. Two boxes of masses m and 2m are in contact with each other on a frictionless surface. What is the acceleration of the more massive box? (In the diagram that is drawn there is a force F touching the box m which is touching box 2m)

A) acceleration due to gravity B)F/m C) F/(2m) D) F/(3M) E) F/(4M)

I chose D and figured that because they are touching, they must be accelerating at the same speed- I didn't think that the force could differentiate between two different boxes that are placed together and a single box equal to both masses added together.

20. A new planet is discovered that has twice the Earth's mass and twice the Earth's radius. On the surface of this new planet, a person who weighs 500 N on Earth would experience a gravitational force of

A) 125 N B)250 N C) 500 N D) 1000 N E)2000 N

We haven't covered this yet, so I have no clue what the answer is.

Free Response Question-

1979B2. A 10-kilogram block rests initially on a table as shown in cases I and II above. The coefficient of sliding friction between the block and the table is 0.2. The block is connected to a cord of negligible mass, which hangs over a massless frictionless pulley. In case I a force of 50 newtons is applied to the cord. In case II an object of mass 5 kilograms is hung on the bottom of the cord. Use g = 10 meters per second squared.

a. Calculate the acceleration of the 10-kilogram block in case I.

b. On the diagrams below, draw and label all the forces acting on each block in case II

c. Calculate the acceleration of the 10-kilogram block in case II.

Part A- I worked it out, said that SimgaF= F(sub tension) - F(friction) = 10 kg a

I think that because in part A, only a force is applied, it is equivalent to the tension force (50 N). I ended up getting 3 m/s^2 for a.

Part C- I gathered equations Sigma F(sub x)= F(tension) - F(friction) = m(sub 1)*(a)

and Sigma F(sub y) = m(sub 2) * gravity - F(tension)= M(sub 2) a

I solved for F(tension in the first equation and plugged that into the second and solved, and got an acceleration of 2 m/s^2

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# Homework Help: Take Home Test (Solved, but Checking Answers) From AP Physics B (Dynamics)

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