3 Physics Questions - Please Pick a Question(s) and explain as many as you can! NOTE: DIFFERENT QUESTIONS!?

Question

1. A ball of mass 0.10 kg moving with speed of 2.0 m/s hits a wall and bounces back with the same speed in the opposite direction. What is the cahnge in the ball's kinetic energy?

2. A shooting star is a meterid that burns up when it reaches Earth's atmosphere. Many of these meteroids are quite small. Calculate the kinetic energy of a meteroid of mass 5.0 g moving at a speed of 48 km/s and compare it to the kinetic energy of a 1100-kg car moving at 29 m/s (65 mi/h).

3. A gymnast of mass 52 kg is jumping on a trampoline. She jumps so that her feet reach a maximum height of 2.5 m abovoe the trampoline and, when she lands, her feet stretch the trampoline down 75 cm. How far does the trampoline stretch when she stands on it at rest?
[Hint: Assume the trampoline obeys Hooke's law when it is streched].

ANSWERS BELOW - Please explain :)

Answer 1

1. No change since the magnitude of velocity is unchanged

2. Comparing the two using .5*m*v^2
.5*5*48^2
vs
.5*1100*29^2

take the ratio
5*48^2/(1100*29^2)

3. Hooke's law states that the force of a spring is
k*x

also the energy is .5*k*x^2
when she lands the potential energy of m*g*2.5
is equal to .5*k*.75^2, so compute k
52*9.81*2.5*2/.75^2=k
to compute the rest compression
m*g=k*x

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