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Homework Help: Estimates on accelerations for different objects

  1. Feb 20, 2015 #1
    1. The problem statement, all variables and given/known data

    Write a “short” entry (at least 5 to 6 sentences) that shows estimates of the accelerations of different objects including a sports car (please specify make and model), a tennis ball serve and an electron in an electric field. Compare and Contrast the accelerations of these objects.

    2. Relevant equations
    force F=qE.

    3. The attempt at a solution
    Electron goes faster than a sports car and a tennis ball serve. A sports car goes 97 km/hr in 3.5 seconds.
    I just don't know how to expand my answer in terms of comparing the accelerations of these objects.
    Last edited: Feb 20, 2015
  2. jcsd
  3. Feb 20, 2015 #2
    did you have a question? (I probably can't help cause I'm not to the point where I've been taught F=qE but I feel like you should specify where your having difficulty, from what u wrote it seems like your getting it)
  4. Feb 20, 2015 #3
    I just don't know how to expand my answer in terms of comparing the accelerations of these objects.
  5. Feb 20, 2015 #4
    for an essay q huh, just throw in every step of your quantitive analysis (right down to a=Δv/Δt), the put in in terms of order of magnitude, and maybe for show throw in some similar velocity realationships people can visualize (such as an electron acc./car acc. is proportional to a jet plane and a turtle, or something)

    you get the physics of it, now you just want to make it sound good, think of how these comparisons would have made sense to you before you took a physics coiurse

    personally I feel its a subjective lame question better suited for an education class, but if you gotta go throw the motions to get the good old essay format out of it going through the motion shouldn't be that hard
  6. Feb 20, 2015 #5
    How about this?

    Electrons accelerate when placed in an electric field (E). An electron placed between a negatively charged cathode and positively charged anode will feel a force F=qE. A particle with mass m to which a force is applied will have an acceleration a=F/m, therefore a particle in an electric field will experience an acceleration a=qE/m.

    A sports car is able to reach 0–100 km/h time or 0–60 mph (0–97 km/h) in 3.5 seconds or less for the first list, or cover quarter mile (402 m) from a standing start in 12 seconds or less.

    Impulse and Momentum are two key biomechanical factors that are used in the tennis serve. Impulse is “the product force, multiplied by the time that a force acts.” Momentum is the product of mass and velocity. So in order to increase an object’s momentum, we need to increase the impulse. In order to increase the momentum of a tennis ball in a serve (increasing it’s speed and velocity), the impulse force of the racquet needs to be increased. Newton’s second law states that: “the acceleration of an object is proportional to the net force acting on it and inversely proportional to the mass of the object: Force=mass X acceleration (F=ma).” Hence, the easiest way to increase the momentum of the tennis ball is to increase the acceleration of the racquet before it makes contact with the ball. This also means increasing the speed of the torso and arms. This allows faster movement of the racquet. The greater the acceleration of the racquet during the wind-up stage, the greater the force in which is applied when connecting with the ball. This will in turn increase the momentum of the tennis ball and increase the speed of the ball.
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