please write clearly thanks S. A ball starting from rest at the top of an inclin

Question

please write clearly thanks

S. A ball starting from rest at the top of an inclined plane accelerates at 4 m/s? and reaches the bottom of the plane in 2 seconds. What is the length of the plane? A. 9 m B. C. 4 m D. 2 m t 2 6. An apple falls from a tree and hits the gro und 20 meters below with a speed of about C. 5 m/s D. not enough information. A. 20 m/s B. 10 m/s 7. At one instant an object in free fall is moving downward at 40 m/s. One second later its speed is A. 60 m/s B. 55 m/s C. 50 m/s D. 30 m/s 8. At one instant a heavy object in air is moving upward at 40 m/s. One second later its speed is approximately A. 30 m/s B. 40 m/s C. 55 m/s D. 60 m/s The distance a freely falling object falls from rest in 2second is A. 60 m 9. B. 40 m C. 20 m D. none of the above An object falls freely from rest on a planet where the acceleration due to gravity is 1 m/s2. After 5 seconds, the object will have a speed of 10. D. 5 m/s A 100 m/s B. 20 m/s C. 10 m/s

Explanation / Answer

5. d = v0 t + a t^2 / 2

d = (0) + (4 x 2^2 / 2)

d = 8 m

Ans(B)

6. vf^2 - vi^2 =2 ad  

v^2 - 0^2 = 2(10)(20)

v = sqrt(2 x 10 x 20) = 20 m/s

Ans(A)

7. vf = vi + a t

v = 40 + (10 x1) = 50 m/s Ans(B)

8. vi = +40 m/s (taking upward positive)

then a = - 10 m/s^2

vf = vi + at

v = 40 + (-10 x 1) = 30 m.s

Ans(A)

9. d = 0 + (10 x 2^2 / 2) = 20 m

Ans(C)

10. v =vi + a t

v = 0 + (1 x 5) = 5 m/s

Ans(D)

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