9). (2 O points) A certain freely falling object, released from rest, requires 1

Question

9). (2 O points) A certain freely falling object, released from rest, requires 1.70 s to travel the last 27.0 m before it hits the ground. (a) Find the velocity of the object when it is 27.0 m above the ground. (a) Find the total distance the object travels during the fall. 10). (20 points) Two train cars are on a straight, horizontal track. One car starts at rest and is put in motion with a constant acceleration of 2.50 m/s2·This car moves toward a second car that is 32.0 m away. The second car is moving away from the first car and is traveling at a constant speed of 4.50 m/s. a) Where will the cars collide? b) How long will it take for the cars to collide?

Explanation / Answer

during last 27m,the time taken is t = 1.7 sec

then using kinematic equations

S = (Vo*t)+(0.5*a*t^2)

a is the accelaration due to gravity = 9.8 m/s^2

27 = (Vo*1.7)+(0.5*9.8*1.7^2)

Vo = 7.55 m/sec is the answer for a)

b) for the entire fall

initial speed is Vo = 0 m/sec

final speed is V = 7.55 m/sec

using

V^2 -Vo^2 = 2*a*S

7.55^2 - 0^2 = 2*9.8*S

S = 7.55^2/(2*9.8) = 2.91 m

so total distance travelled is 2.91+27 = 29.91 m

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