A 5.0 kg object with speed of 4.0 m/s collides head-on with a 10 kg object movin

Question

A 5.0 kg object with speed of 4.0 m/s collides head-on with a 10 kg object moving towards it with speed of 3.0 m/s. The 10 kg object stops after the collision, (a) What the post collision speed of the 5.0 kg object? (b) Is the collision elastic? (8 - 55) There is a 250-m-high cliff at Half Dome in Yosemite National Park in California. Suppose a boulder breaks loose from the top of this cliff. (a) How fast will it be going when it strikes the ground? (b) Assuming a reaction time of 0.300 s, how long will a tourist at the bottom have to get out of the way after hearing the sound of the rock breaking loose (neglecting the height of the tourist, which would become negligible anyway if hit)? The speed of sound is 335 m/s on this day. [35 - 20] A 5.00 times 10^5 -kg rocket is accelerating straight up. Its engines produce 1.250 times 10^7 N of thrust, and air resistance is 4.50 times 10^6 N. What is the rocket's acceleration? Explicitly show how you follow the steps in the Problem-Solving Strategy for Newton's laws of motion. [32 - 40] bullet of mass m_1 is fired horizontally with speed v into a block of a ballistic pendulum of mass m_2. Find the maximum height h which the block will attain if the bullet passes through the block and emerges with a speed of v/3. (8 - 67]

Explanation / Answer

1)
m1 = 5 Kg

u1 = 4 m/s

m2 = 10 Kg

u2 = -3 m/s

v2 = 0 m/s

a) let the speed of the 5 Kg is v1

Using conservation of momentum

m1 * u1 + m2 * u2 = (m1 + m2) * v

4 * 5 - 3 * 10 = (5) * v

solving for v

v = -2 m/s

the speed of 5 Kg post collision is 2 m/s

b)

coefficient of resitition = relative speed after collision/relative speed before collision

coefficient of resitition = (2)/(4 + 3)

coefficient of resitition = 2/7

hence , the collision is not elastic

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