Kinematics & Forces
AP PHYSICS 1
Name:_______________
Free Response (FR) Questions: Below are two (2) short FR questions. You should allow approximately 10 minutes
for each problem.
FR 1:
A substitute teacher for your class claims to have a new formula that will “save you time” when solving for final
velocity. They offer the formula that follows:
𝑣=
𝐹∙𝑡
𝑚
In this proposed formula, v = final velocity, F = the force on the object, t = the time interval over which the force
was acting, and m = the mass of the object.
Being as clear and concise as possible, prepare a paragraph-length discussion about whether or not you feel this
formula is reasonable for determining the final velocity of an object undergoing a force. Qualitatively explain your
reasoning, making sure you address the formula’s (and thus the velocity’s) proposed dependence on F, t, and m.
Kinematics & Forces
AP PHYSICS 1
Name:_______________
FR 2:
A small rocket ship with a mass of 1000 kg is resting on a Florida launch-pad. At 10 seconds, the engines ignite,
producing a constant thrust of 100,000 N. The launch proceeds smoothly and rocket climbs vertically for another
10 seconds before the thrusters momentarily switch off for 5 seconds. Then a stronger thruster kicks in, producing a
constant thrust of 200,000 N until it leaves the atmosphere several minutes later.
(a) On the following diagram, sketch the acceleration vs time chart for the rocket from t = 0 until t = 30s.
(no absolute values for acceleration are necessary, only relative magnitudes)
a
0s
5s
10s
15s
20s
25s
30s
t
(b)
i)
During the launch, the force on the launch-pad is carefully monitored by engineers. During the 10
second countdown before the thrusters ignited, the force reading was 9800 N. Once the engines ignited,
and the rocket just began to lift off, how did the force reading on the launch-pad momentarily change?
(check one)
___ less than 9800 N
ii)
Justify your answer.
___ stayed at 9800 N
____ greater than 9800 N