Question

10) The velocity (t) of a particle as a function of time is given by (h) - 023 m/s) (4.1 m/s2)+- (62 m/s3)2. What is the average acceleration of the particle between t = 10 s and t - 205? A) - 15 m/s2 B ) 15 m/s2 C) -13 m/s2 D) O m/s2 E) 13 m/s2 11) A car starts from rest and accelerates uniformly at 3.0 ms2 toward the north. A second car starts from rest 60 s later at the same point and accelerates uniformly at 5.0 m/s2 toward the north. How long after the second car starts does it overtake the first car? A) 19 5 B) 24 5 C215 D) 125 12) If a satellite moves with constant speed in a perfectly circular orbit around the earth, what is the direction of the acceleration of the satellite? A) outward away from the earth B) in the backward direction C) inward toward the earth D) in the forward direction E) The acceleration is zero because the speed is constant 13) You are trying to cross a river that flows toward the south with a strong current. You start out in your motorboat on the east bank desiring to reach the west bank directly west from your starting point. You should head your motorboat A) in a general southwesterly direction. B) in a general northwesterly direction C) directly toward the north D ) directly toward the west. 14) Consider two vectors A and B shown in the figure. The difference A - B is best illustrated by (a) (b) A) choice (a) (c) B) choice (b) C) choice (c) D) choice (d) 15 15) A ball thrown horizontally from a point 24 m above the ground strikes the ground after traveling horizontally a distance of 18 m. With what speed was it thrown, assuming negligible at resistance? A) 8.9 m/s B) 7.4 m/s C) 8.1 m/s D) 6.1 ms 18 16) A boy throws a rock with an initial velocity of 3.13 m/s at 300 above the horizontal How long does it take for the rock to reach the maximum height of its trajectory if air resistance is negligibly small and g - 980 m/s2? A) 0.3135 B) 0.1605 C) 0.282 D) 0.4413 17 17) A plane flying horizontally at a speed of 50 m/s and at an elevation of 160 m drops a package and 20 s later it drops a second package. How far apart will the two packages and on the ground fair resistance is negligible? A) 180 m B) 100 m 320 m D) 160 m

Answer 1

10) A) 15 m/s^2

given

v(t) = 2.3 + 4.1 t - 6.2 t^2

at time t1 = 1 s,

v1 = 2.3 + 4.1*1 - 6.2*1^2

= 0.2 m/s

at time t = 2 s

v2 = 2.3 + 4.1*2 - 6.2*2^2

= -14.3 m/s^2

average acceleration between t = 1 s to t = 2s

a_avg = (v2 - v1)/(t2 - t1)

= (-14.3 - 0.2)/(2 - 1)

= -14.5 m/s^2

= -15 m/s^2 (when rounded to two significant figures)