A tennis racket hits a tennis ball with a force of F=at−bt2, where a = 1200 N/ms , b = 370 N/ms2 , and t is the time (in millise
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Answer:
v = 28.7 m/s
Explanation:
- According to the Work Energy Theorem, the work done by external forces on the system, is equal to the change in the kinetic energy of the system.
- In absence of friction, the only force that does work , producing a displacement in the direction of the force, is the component of gravity parallel to the slide:
- The displacement d,along the slide, can be found from the definition of the sine of an angle, as follows:
- Solving for d, we get:
- Now, the work done by Fgp, is just the product of the force times the displacement, as follows:
- From (1) and (2) we can find W as follows:
- This expression must be equal to ΔK, as follows:
- Simplifying common terms, we can solve for v (the velocity of the sled at the bottom of the slide), as follows:
- The velocity of the sled at the bottom of the slide is 28.7 m/s, taking as positive the direction down the slide.
Answer:
140 J
Explanation:
From the the question, the mass of the man =70.0 kg and the speed at which the man is walking =2.0 m/s.
where K.E = the kinetic energy, m=mass and v= speed.
By substitution,
Hence the kinetic energy of the man is 140J