# ES 204- Dynamics

ES 204- Dynamics

## Concept problems

Concept Problem 1:

The example from, Physics of Basketball – Hang Time (Links to an external site.) (Real-world physics), describes the physics of basketball. What is the maximum height of the basketball when the player passes the ball to someone? Initially, the ball moves at a speed of 12m/sec at an angle with respect to the horizontal of 45 degrees. Is it possible that the other player standing 8m away is able to catch the ball without any bounces?

Concept Problem 2:

Concept Problem 3:

A car with a mass of 1200 kg, traveling at 60 ft/sec, brakes to a stop within 40 ft. Assume that the braking force is constant during that phase. A truck, 20 times as heavy as the car, is employing the same braking force. What will the truck’s stopping distance be when traveling at the same speed? If the truck needs to stop also within 40 ft, what statement can you make about the energy dissipation by the brakes? How can you figure the temperature rise by the brakes? Provide your explanation using the principle of work and energy.

Concept Problem 4:

Two boxes are initially at rest on a horizontal frictionless surface.  One box has twice the mass as the other. A loaded spring, fixed only to one box, connects in line through both center of masses. The spring is released: What is the relationship of the velocities of these boxes after the spring is un-loaded? What is the relationship of the momenta of both boxes? Now assume friction with a constant μ between the boxes and the ground. Discuss possible outcomes. Look up what a “Slip-Stick” Effect is, and expand on that. Also, watch the video Stick-Slip Motion (01:06/YouTube). (Links to an external site.)

Concept Problem 5:

What happens to the acceleration and velocity of an Apache helicopter when it fires a rocket-propelled missile at an enemy tank in front of it? How about the torque exerted by the missile? After launching a missile, will the helicopter’s speed be faster, slower, or stay the same? Does the pilot have to correct for pitch, yaw, or roll? Provide your reasoning. What parameters would you need to figure those accelerations?

Concept Problem 6:

Concept Problem 7:

Concept Problem 8:

Concept Problem 9:

A mass M is horizontally attached to a spring with a spring constant k. Let’s consider two different inputs:

a) A sudden step force F0 in the downward direction. Analyze the resulting motion, like amplitude and mean value. Now include a damper: How can you find an engineering characterization of a “Damper”? What will the final displacement be, when including the damper? (System at rest)

b) An oscillatory force F = A ⋅ sin ⁡ ( ω t )will be applied. Perform the same analysis as in a), but exclude the damper. Explain what “Resonance” means. Find “real world” engineering applications (or engineering disasters) induced by resonances.

Provide your reasoning. Your initial response must be a minimum of one or two paragraphs and the responses to your peers should be a minimum of 50 words. You are also required to reply to one response on your initial post.