The spring shown in the figure is compressed 56 cm and used to launch a 100 kg p
ID: 1788341 • Letter: T
Question
The spring shown in the figure is compressed 56 cm and used to launch a 100 kg physics student. The track is frictionless until it starts up the incline. The student's coefficient of kinetic friction on the 30 incline is 0.18 . (Figure 1)
What is the student's speed just after losing contact with the spring?
Express your answer to two significant figures and include the appropriate units.
v =
How far up the incline does the student go?
Express your answer to two significant figures and include the appropriate units.
s =
80,000 N/m m 100 kg k 10 m 30°Explanation / Answer
Applying energy conservation for spring-student system,
k x^2 /2 = m v^2 /2
80,000 (0.56^2) = 100 v^2
v = 15.8 m/s ..........Ans
Speed at bottom,
m g (10) + m (15.8^2 /2) = 0 + m v^2 /2
v = sqrt( (2 x9.8 x 10) + 15.8^2)
v = 21.1 m/s
perpendiculat to incline, N = m gcos30
f = uk N = 0.18 m g cos30
along the incline,
- 0.18 m g cos30 - m g sin30 = m a
a = - 6.43 m/s^2
vf^2 - vi^2 = 2 a d
0^2 - 21.1^2 = 2(-6.43)d
d = 34.6 m .......Ans
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