A child is playing with their Hot Wheel cars. They have set up a track which is
ID: 1553904 • Letter: A
Question
A child is playing with their Hot Wheel cars. They have set up a track which is initially horizontal but then ascends to a second horizontal section which is 50 cm higher than the initial track. The track is frictionless until the car reaches the upper section of the track where some spilled soft drink exerts a frictional force on the car. They launch the 100 gram cars on the lower horizontal section using a spring loading launcher which requires the spring to be compressed by 2 cm. (Use conservation of energy and work to solve this problem.)
a. If the car is travelling at 1 m/s when it initially reaches the upper section of the track what is the spring constant of the launcher?
b. If the coefficient of kinetic friction on the upper portion of the track is 0.4, how far does the car travel before it stops?
c. Draw energy bar charts for: i. The initial situation (the car is in the spring loading launcher with the spring compressed), ii. When the car arrives at the start of the upper horizontal section, iii. When the car comes to a final stop.
d. What work does the child need to do to compress the spring?
e. How much work does the frictional force do? Note: for questions d and e you should be able to determine answers without doing detailed calculations and use information already calculated in parts a to c.
Explanation / Answer
a) energy conservation
(1/2) kx2 =mgh +1/2 mV2
1/2 *k *4 *10-4 = 0.1 *9.8 *50*10-2 + 1/2 * 0.1 *12
K= 2700 N/m
B) work = change oin K.E
0.4(N) *x = 1/2 *m*V2
0.4* mg *x = 1/2 *m*V2
0.4gx = v2 /2
x = 13.89 cm
D) work done by child = stored energy = 1/2 K *x2
= 1/2 *2700*2500*10-4 = 337.5 j
E) we already calculated in part b
work = change in K.E = 1/2 m *v2 = 1/2 *0.1*1*1 = 0.05 j
C) i dont understant what kind of bar graph you wanted
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