AP Physics 1 FRQ Practice

🎡AP Physics 1

Practice FRQ 1 of 171/17

1. A student stands on a straight, level sidewalk next to a long train moving in a straight line. At the instant the student is next to a particular window on the train, a ball is launched from the window, as shown in Figure 1. Neglect air resistance.

Figure 1. Ball launched from a train window: ground frame axes, train speed v_T, launch speed v_0 at angle θ, and window height y_0 above the sidewalk.

Figure 2. Axes for sketching the ball’s x-component of velocity v_x versus time t (student/sidewalk frame).

On the axes shown in Figure 2, sketch a graph of the x-component of the velocity $v_x$ of the ball as a function of time $t$ as measured by the student from $t = 0$ until $t > t_2$ .

ii.

Derive an expression for the x-component $v_{x,S}$ of the ball's velocity as measured by the student immediately after launch in terms of $v_T$ , $v_0$ , and $\theta$ . Begin your derivation by writing a fundamental physics principle or an equation from the reference information.

iii.

Derive an expression for the time $t_2$ at which the ball reaches the ground as measured by the student in terms of $y_0$ , $v_0$ , $\theta$ , $g$ , and physical constants, as appropriate. Begin your derivation by writing a fundamental physics principle or an equation from the reference information.

Indicate whether the magnitude of the ball's velocity measured by the sidewalk student at $t = 0.50\ \text{s}$ is greater than, less than, or equal to the magnitude measured by the train student. Consider a second student who is riding on the train and is at rest in the train's reference frame. Both the sidewalk student and the train student are in inertial reference frames. Assume the train moves with constant velocity for the entire motion.

At a time $t = 0.50\ \text{s}$ after launch, the train student measures the ball's velocity to have magnitude $8.00\ \text{m/s}$ at an angle $20.0^\circ$ above the horizontal.

Greater than
Less than
Equal to
Justify your response.