(Questions 1,2,3 not related) One. When a horizontal force of 320 N is applied t
ID: 2168571 • Letter: #
Question
(Questions 1,2,3 not related)One. When a horizontal force of 320 N is applied to a 78.0 kg box, the box slides on a level floor, opposed by a force of kinetic friction of 150 N. What is the magnitude of the acceleration of the box?
Two. A sprinter of mass 65.1 kg starts his race by pushing horizontally backward on the starting blocks with a force of 240 N.
a. What force causes him to accelerate out of the blocks? (Circle 1, 2, or 3)
1. The force the block exerts on him.
2. The downward force of gravity.
3. His push on the blocks.
b. What is the acceleration of the sprinter?
Three. A 71-kg man stands on a bathroom scale in an elevator. What does the scale read if the elevator is ascending with an acceleration of 3.0 m/s2?
Explanation / Answer
(Q1) a =(F-fr)/m = (320-150)/78 = 2.18m/s2 Ans. (Q2) 1. The force the block exerts on him. a= F/m = 240/65.1 = 3.686m/s2 Ans. (Q3) in non inertial frame of reference, new acceleration = g-a so, F =m(g-a) = 71(9.8-3) = 482.8N Ans.
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