A particle moves 70 m west, then moves 120 m east, and finally moves east again

Question

A particle moves 70 m west, then moves 120 m east, and finally moves east again a distance of 90 m. If ea is chosen as the positive direction, what is the particle's resultant displacement? 40 m -40 m 280 m 140 m A particle moves 20 m east in 10 s and then returns to its starting point taking an additional 30 s. If east is chosen as the positive direction, what is the average speed of the particle? 0.50 m/s -0.50 m/s 2.66 m/s 1.0 m/s A ball is pushed with an initial velocity of 4.0 m/s. The ball rolls down a hill with a constant acceleration 1.5 m/s^2. The ball reaches the bottom of the hill in 8.0 s. What is the ball's velocity at the bottom of the hi 10 m/s 12 m/s 16 m/s 17 m/s A bird, accelerating from rest at a constant rate, experiences a displacement of 28 m in 4 s. What is the fi velocity after 4 s? 1.8 m/s 3.5 m/s 14 m/s zero A drag racer starts from rest and accelerates at 18 m/s^2 for the entire distance of 400 m (approximately, mile). What is the velocity of the race car at the end of the run? 45 m/s 89 m/s 120 m/s 180 m/s If the displacement of an object is given in SI units by delta x = -12t + 2t^2, at t = 2 s its velocity and are, respectively: positive, positive positive, negative negative, negative negative, positive A rock is thrown straight up with an initial velocity of 14.0 m/s. What maximum height will the rock before starting to fall downward? (Take g equal to 9.80 m/s^2.) 14.3 m 10.0 m

Explanation / Answer

1. r1 = - 70 m

r2 = 120 m

r3 = 90 m

r = r1 + r2 + r3 = 140 m

Ans(d)

2. total distance = 20 + 20 = 40 m

total time taken = 10 + 30 = 40s

<v> = 40/40 = 1 m/s

Ans(d)

3. v = u + a t

v = 4 + 1.5x8 = 16 m/s

Ans(C)

4. d = u t + a t^2 / 2

28 = 0 + a (4^2)/2

a = 3.5 m/s^2

v = u + at = 0 + (3.5 x 4) = 14 m/s

Ans(C)

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