The next two questions are worth 20 points in total. For both questions, conside

Question

The next two questions are worth 20 points in total. For both questions, consider the following: A 5 kg and 8 kg block are on a horizontal table. The 5 kg block is initially at rest and the 8 kg block is initially moving directly toward the 5 kg block with m velocity 4 m/s. The two blocks stick together and slide off the table. You want to determine the speed of the blocks immediately before they hit the ground. You may assume that the blocks lose no energy due to friction with the table or by air resistance. 17. (8 points) What is the speed of the blocks immediately after they collide? A. 2.46 m/s B. 6.40 m/s C. 10.7 M/s D. 3.14 m/s E. 4.48 m/s 18. (12 points) What is the speed of the blocks immediately before they hit the ground? A. 3.43 m/s B. 4.22 m/s C. 4.65 m/s D. 7.26 m/s E. 2.39 m/s

Explanation / Answer

here,

mass of block 1 , m1 = 5 kg

mass of block 2 , m2 = 8 kg

initial speed of block 2 , u2 = 4 m/s

17.

let the the final speed of blocks be vx

using conservation of momentum

m2 * u2 = (m1 + m2) * vx

8 * 4 = (8 + 5) * vx

vx = 2.46 m/s

the speed after the masses collide is A. 2.46 m/s

18.

height of table , h = 0.6 m

initial vertical velocity , uy = 0

let the vertical velocity when mass hits the ground be vy

using third equation of motion

vy^2 + uy^2 = 2 * g * h

vy^2 = 2 * 9.8 * 0.6

vy = 3.43 m/s

let speed of blocks when they hit the ground be v

v = sqrt(vx^2 + vy^2)

v = sqrt (2.46^2 + 3.43^2)

v = 4.22 m/s

speed of blocks immediately before they hit the ground is B. 4.22 m/s

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