2019年AP物理1简答题真题+答案+PDF下载

1.(7 points, suggested time 13 minutes)

Identical blocks 1 and 2 are placed on a horizontal surface at points A and E, respectively, as shown. The surface is frictionless except for the region between points C and D, where the surface is rough. Beginning at time t_{A} ,block 1 is pushed with a constant horizontal force from point A to point B by a mechanical plunger. Uponreaching point B, block 1 loses contact with the plunger and continues moving to the right along the horizontalsurface toward block 2. Block 1 collides with and sticks to block 2 at point E, after which the two-block systemcontinues moving across the surface, eventually passing point F.

(a)On the axes below, sketch the speed of the center of mass of the two-block system as a function oftime, from time t_{A} until the blocks pass point F at time t_{F}. The times at which block 1 reaches points A through F are indicated on the time axis.

(b)The plunger is returned to its original position, and both blocks are removed. A uniform solid sphere isplaced at point A, as shown. The sphere is pushed by the plunger from point A to point B with a constanthorizontal force that is directed toward the sphere’s center of mass. The sphere loses contact with theplunger at point B and continues moving across the horizontal surface toward point E. In which interval(s),if any, does the sphere’s angular momentum about its center of mass change? Check all that apply.

____A to B ____B to C ____C to D ____D to E _____None

Briefly explain your reasoning.

2. (12 points, suggested time 25 minutes)

This problem explores how the relative masses of two blocks affect the acceleration of the blocks. Block A, of mass m_{A}, rests on a horizontal tabletop. There is negligible friction between block A and the tabletop. Block B, of mass m_{B}, hangs from a light string that runs over a pulley and attaches to block A, as shown above. The pulley has negligible mass and spins with negligible friction about its axle. The blocks are released from rest.

(a)

i. Suppose the mass of block A is much greater than the mass of block B. Estimate the magnitude of the acceleration of the blocks after release.

Briefly explain your reasoning without deriving or using equations.

ii. Now suppose the mass of block A is much less than the mass of block B. Estimate the magnitude of the acceleration of the blocks after release.

Briefly explain your reasoning without deriving or using equations.

(b) Now suppose neither block’s mass is much greater than the other, but that they are not necessarily equal.The dots below represent block A and block B, as indicated by the labels. On each dot, draw and label the forces (not components) exerted on that block after release. Represent each force by a distinct arrow starting on, and pointing away from, the dot.

(c) Derive an equation for the acceleration of the blocks after release in terms of m_{A}, m_{B}, and physicalconstants, as appropriate. If you need to draw anything other than what you have shown in part (b) to assistin your solution, use the space below. Do NOT add anything to the figure in part (b).

(d)Consider the scenario from part (a)(ii), where the mass of block A is much less than the mass of block B.Does your equation for the acceleration of the blocks from part (c) agree with your reasoning in part (a)(ii) ?

____Yes ____No

Briefly explain your reasoning by addressing why, according to your equation, the acceleration becomes (or approaches) a certain value when m_{A} is much less than m_{B}.

(e)While the blocks are accelerating, the tension in the vertical portion of the string is T_{1}. Next, the pulley ofnegligible mass is replaced with a second pulley whose mass is not negligible. When the blocks areaccelerating in this scenario, the tension in the vertical portion of the string is T_{2}. How do the two tensionscompare to each other?

____T_{2}＞T_{1} ____T_{2}＝T_{1} ____T_{2}＜T_{1}

Briefly explain your reasoning.

2019年AP物理1简答题真题余下省略！

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