If ail object moves with constant acceleration, Its velocity must Twelve seconds

Question

If ail object moves with constant acceleration, Its velocity must Twelve seconds after starting from rest, an object falling freely will have a speed of A ball is thrown 125 meters upward and then falls the same distance back to Earth. Neglecting air resistance, its total time in the air is A car accelerates at 2 meters per second per second. Assuming the car starts from rest, how much time does it need to accelerate to a speed of 30 m/s? When a rock thrown straight upwards gets to the exact top of its path, its

Explanation / Answer

9)

Ans: E) distance and time

Reason: Use equation,

speed= distance/time

10)

Ans: change by the same amount each second

Reason: Use equation,

acceleration= v/t

When acceleration is constant

v= a*t = a*1s = a

Thus change is constant.

11)

vf=vi –gt = 4.9 -9.8*2 = -14.2 m/s

|vf|= 14.9m/s

Ans: B) 14.9 m/s

12)

vf=vi –gt = 0 -9.8*12 = -117.6 m/s

|vf|= 117 m/s

Ans: C) More than 100 m/s

13)

Use equation at the max height,

h= vi*t -1/2gt^2

-125 = 0*t – ½*9.8*t^2    => t=5.05s

Total time , T= 2t = 10.1s

Ans: A) about 10seconds

14) a= 2m/s^2

Vf= vi+at

30 = 0 + 2*t

t=15s

Ans: A) 15 seconds

15)

Ans: A) velocity is zero and acceleration is about 10 meters per second per second.

Reason: rock is in the free fall motion. In free fall acceleration is equal to 10m/s^2

And at max height velocity = 0 m/s

16)

Ans: D) 0

Reason: Since object covers same distance in equal time interval it is moving with constant velocity.

When the velocity is constant acceleration is zero.

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