physics sttes 1. A toy gun is pointed toward the sky. A stvrofoam ball of mass 1

Question

physics

sttes 1. A toy gun is pointed toward the sky. A stvrofoam ball of mass 10g is at rest against a spring compressed 2cm. The spring is released causing the ball to move upward through the air to a max height of Im. The air exerts a frictional force of 0.35N on the ball. What is the spring constant of the spring? 2. A pool ball of mass 0.15kg travels at 3m/s in the +s direction. It strikes another pool ball of mass 0.17kg that is at rest. Assuming that the collision is elastic, what is the velocity of each ball after the collision? 3. A red bumper car of 500kg traveling at 7m/s in the #x direction collides with a blue bumper car of 750kg traveling at 9m/'s in the -x direction. After the collision the red car is traveling at 8.5m/s in the -x direction, what is the velocity of the blue car after the collision?

Explanation / Answer

1. mass m = 10g = 10-2 Kg

compression x = 2cm = 2 x 10-2 m

height h = 1 m

frictional force f = 0.35 N

work done by the frictional force w = f . h = 0.35 x 1 = 0.35 J

from conservation of energy

0.5 k x2 = mgh + w

  k x2 = 2 mgh + 2w

= 2 x 10-2 x 9.81 x 1 + 2x.35

k ( 4 x 10-4 ) = 0.8962

k = 2240 N/m

2. m1 = 0.15kg u1 = 3m/s

m2 = 0.17 kg u2 = 0

velocity of m1 after collission v1 = (m1 - m2) u1 /( m1 + m2 )  

=( 0.15 - 0.17) 3/(0.15+0.17)

= -0.19 m/s

negative sign indicates it moves in -x direction after collission

similarly v2 = 2m1u1/(m1+m2)

= 2 x 0.15 x3/0.32

= 2.8 m/s

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