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Fundamentals Of Physics
Found in: Page 170

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Short Answer

A proton (mass m=1.67×10-27 kg) is being accelerated along a straight line at 3.6×1015 m/s2 in a machine. If the proton has an initial speed of 2.4×107 m/s and travels 3.5 cm, what then is (a) its speed and (b) the increase in its kinetic energy?

  1. The final speed of the proton is 2.9×107 m/s.
  2. The increase in the kinetic energy of the proton is 2.1×10-13 J.
See the step by step solution

Step by Step Solution

Step 1: Given data

  1. Mass of the proton is, m=1.67×10-27 kg.
  2. Acceleration is, a=3.6×1015 m/s2.
  3. The initial speed is, vi=2.4×107 m/s.
  4. Distance traveled is, d=3.5 cm=0.035 m.

Step 2: Understanding the concept

Using the third kinematic equation, we can find the final speed of the proton from a given mass, acceleration, and initial speed of the proton. Also, we can use this final velocity and given initial velocity to calculate the increase in its kinetic energy.

Step 3: a) Calculate the speed of the proton

From newtons law of motion equations, the final velocity can be calculated as,

vf2=vi2+2ad

Substitute the given values in the above equation, and we get,

vf2=2.4×107ms2+23.6×1015 ms20.035 mvf2=5.76×1014 m2/s2+2.52×1014 m2/s2 vf2=8.41×1014 m2/s2vf=2.9×107 m/s

Therefore, the final speed of the proton is 2.9×107 m/s.

Step 4: (b) Calculate the increase in the proton’s kinetic energy 

The expression for kinetic energy is,

K=12mv2

Initial kinetic energy can be calculated as,

Ki=12mvi2

Substitute the given values in the above equation, and we get,

Ki=121.67×10-27 kg2.4×107 ms2=4.8×10-13.1 kg×1m2s2×1 J1 N.m×1 N1 kg.ms2=4.8×10-13 J

Final kinetic energy can be calculated as,

Kf=12mvf2

Substitute the given values in the above equation, and we get,

Kf=121.6×10-27 kg2.9×107 ms2=6.9×10-13.1 kg×1m2s2×1 J1 N.m×1 N1 kg.ms2=6.9×10-13 J

Therefore, an increase in the kinetic energy of the proton can be calculated as,

K=Kf-Ki

Substitute the given values in the above equation, and we get,

K=6.9×10-13 J-4.8×10-13 JK=2.1×10-13 J

Therefore, an increase in the kinetic energy of the proton is 2.1×10-13 J.

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