Two average forces. A steady stream of 0.213 kg snowballs is shot perpendicularl
ID: 1600237 • Letter: T
Question
Two average forces. A steady stream of 0.213 kg snowballs is shot perpendicularly into a wall at a speed of 4.80 m/s. Each ball sticks to the wall. The figure gives the magnitude F of the force on the wall as a function of time t for two of the snowball impacts. Impacts occur with a repetition time interval Delta t_r = 52.0 ms, last a duration time interval Delta t_d = 12.0 ms, and produce isosceles triangles on the graph, with each impact reaching a force maximum F_max = 170 N. During each impact, what are the magnitudes of (a) the impulse and (b) the average force on the wall? (c) During a time interval of many impacts, what is the magnitude of the average force on the wall?Explanation / Answer
(a)
Since the graph is a triangle, the impulse = average force * time
85 * 12 ms = 1.020N-s = 1.020 kg-m/s
impulse = change in momentum = 0.213 kg *4.80 m/s =1.022 kg-m/s
(b)
the average force on the wall? Since the graph is a triangle, average force = maximum / 2
Fmax/2 = 170N/2 = 85 N
average force = impulse / time = 1.022 kg-m/s / 12 ms = 85.2 N
(c)
average force over 52 ms = impulse / 52 ms = 1.022 kg m/s / 52 ms = 19.65 N