Co 17) An object in mechanical equilibrium is an object 17) A) at rest. C) havin

Question

Co 17) An object in mechanical equilibrium is an object 17) A) at rest. C) having no acceleration. B) moving with constant velocity. D) all of these 18) If a projectile is fired straight up at a speed of 10 m/s, the time it takes to reach the top of its path is 18) about A) 1 second C) 10 seconds B) 2 seconds. D) not enough information to estimate 19) If an object falling freely were somehow equipped with an odometer to measure the distance it 19) travels, then the amount of distance it travels each succeeding second would be A) doubled. C) less and less each second. B) greater than the second before. D) constant. 20) An apple falls from a tree and hits the ground 5 meters below. It hits the ground with a speed of 20) about A) 10 m/s. B) 15 m/s C) 20 m/s D) 5 m/s. E) not enough information given to estimate

Explanation / Answer

17.

If force on body is zero, then object will be in mechanical equilibrium

F = m*a

when at rest, a = 0

when constant speed, a = 0

Also in c option, a = 0

Correct option is D.

18.

v = u + a*t

t = (v - u)/a

a = -g = -10

t = (0 - 10)/(-10) = 1 sec

Correct option is A.

19.

h = u*t + 0.5*g*t^2

in 1st second

h1 = 0*1 + 0.5*10*1^2

h1 = 5 m

till 2 sec

h2 = 0*2 + 0.5*10*2^2

h2 = 20 m

So in 2nd second, distance traveled = 20 - 5 = 15 m

which means distance will be greater than the second before.

Correct option is B.

20.

v^2 = u^2 + 2*a*s

a = g = 10 m/sec^2

v = sqrt (0^2 + 2*10*5) = 10 m/sec

Correct option is B.

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