She does work from the moment she touches the book until she lets it go. Work is anything that requires energy. Therefore, she is working as she picks up the book, carries it, and when she is lifting it onto the shelf.

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A 57-gram tennis ball moving at 70 miles per hour is hit with a 110-gram tennis racquet moving at 60 miles per hour. Which state

Whitepunk [10]

Answer:

D. Because mass and energy are both conserved, the total amounts of mass and energy are the same before and after impact.

Explanation:

As we know that, the energy in motion is Kinetic Energy mathematically given as:

$KE=\frac{1}{2} m.v^2$

Now, according to the law of conservation of energy:

$\frac{1}{2} m_1.u_1^2+\frac{1}{2} m_2.u_2^2=\frac{1}{2} m_1.v_1^2+\frac{1}{2} m_2.v_2^2$

where:

$m_1\ \&\ m_2$ mass of racquet and ball respectively and $u_1\ \&\ u_2$ are their respective initial velocities.

$v_1\ \&\ v_2$ are the respective final velocities.

Also the law of conservation of momentum is applicable in this case:

$m_1.u_1+ m_2.u_2= m_1.v_1+m_2.v_2$

In this case the velocity of the lighter mass will get increases in the final condition.

5 0

2 years ago