Use energy conservation to find the approximate final speed of a basketball dropped from a height of 2m (roughly the height of a professional basketball player). Why don't you need to know the mass of the basketball?

Short Answer

Expert verified

The final speed of the basketball is 6.26m/s. The final velocity does not dependent on mass, so the mass of basketball is not required.

Step by step solution

01

Relation between the ball’s potential and kinetic energy

If the ball is dropped from a height of 2mdetermines the approximate final speed of the ball.

Apply the energy conservation law. Explain why the value of mass is not needed.

Energy cannot be created or destroyed, according to the rule of conservation of energy. It can only be transferred from one type of energy to another.

The ball generates potential energy while losing kinetic energy as it hits the ground. As a result, the kinetic energy loss can be calculated using the formula,

role="math" localid="1657704999970" KE=m21v2

Further, the gain in potential energy can be expressed as,

PE=mgh

As per the law of conservation,

KE=PE
02

Determine the formula from the relation for speed

If we break down the formula above, we can discover the formula for calculating speed.

KE=PE12mv2

KE=mgh12v2

=ghv

=2gh

gis the acceleration due to gravity is equal to 9.8m/s2and his the height. Substitute the given values to the formula.

v=2gh

=29.8m/s2(2.0m)

=6.26m/s

Therefore, the approximate final speed of the ball is 6.26m/s Because the final speed is independent of the ball's mass, the mass is not required. That is, we can still calculate the speed value without it.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Figure 6.76 shows the path of a comet orbiting a star.

(a) Rank-order the locations on the path in terms of the magnitude of the comet’s momentum at each location, starting with the location at which the magnitude of the momentum is the largest. (b) Rank-order the locations on the path in terms of the comet’s kinetic energy at each location, starting with the location at which the kinetic energy is the largest. (c) Rank-order the locations on the path in terms of the potential energy of the system at each location, largest first. (d) Rank-order the locations on the path in terms of the sum of the kinetic energy and the potential energy of the system at each location, largest first

The escape speed from an asteroid whose radius is10 Kmis only 10 m/s . If you throw a rock away from the asteroid at a speed of 20 m/s, what will be its final speed?

You throw a ball straight up, and it reaches a height of20 mabove your hand before falling back down. What was the speed of the ball just after it left your hand?

A ball of massfalls downward, as shown in Figure 6.82. Initially you observe it to beabove the ground. After a short time it is just about to hit the ground.

(a) During this interval how much work was done on the ball by the gravitational force? (b) Does the kinetic energy of the ball increase or decrease?

(c) The ball hits the ground and bounces back upward, as shown in Figure 6.83. After a short time it isabove the ground again. During this second interval (between leaving the ground and reaching a height of) how much work was done on the ball by the gravitational force? (d) Does the kinetic energy of the ball increase or decrease?

A proton(H1)and a deuteron ((H2), “heavy” hydrogen) start out far apart. An experimental apparatus shoots them toward each other (with equal and opposite momenta). If they get close enough to make actual contact with each other, they can react to form a helium-3nucleus and a gamma ray (a high-energy photon, which has kinetic energy but zero rest energy):H1+2H3He+y

This is one of the thermonuclear or fusion reactions that takes place inside a star such as our Sun.

The mass of the proton is 1.0073 u(unified atomic mass unit,1.7×10-27kg), the mass of the deuteron is 2.0136 u, the mass of the helium-3nucleus is 3.0155 u, and the gamma ray is massless. Although in most problems you solve in this course it is adequate to use values of constants rounded to two or three significant figures, in this problem you must keep at least six significant figures throughout your calculation. Problems involving mass changes require many significant figures because the changes in mass are small compared to the total mass. (a) The strong interaction has a very short range and is essentially a contact interaction. For this fusion reaction to take place, the proton and deuteron have to come close enough together to touch. The approximate radius of a proton or neutron is about1×10-15m. What is the approximate initial total kinetic energy of the proton and deuteron required for the fusion reaction to proceed, in joules and electron volts (1eV=1.6×10-19J)? (b) Given the initial conditions found in part (a), what is the kinetic energy of theHe3plus the energy of the gamma ray, in joules and in electron volts? (c) The net energy released is the kinetic energy of theHe3plus the energy of the gamma ray found in part (b), minus the energy input that you calculated in part (a). What is the net energy release, in joules and in electron volts? Note that you do get back the energy investment made in part (a). (d) Kinetic energy can be used to drive motors and do other useful things. If a mole of hydrogen and a mole of deuterium underwent this fusion reaction, how much kinetic energy would be generated? (For comparison, aroundare obtained from burning a mole of gasoline.) (e) Which of the following potential energy curvesin Figure 6.87 is a reasonable representation of the interaction in this fusion reaction? Why?

As we will study later, the average kinetic energy of a gas molecule is32kbT, whereis the “Boltzmann constant,”1.4×10-23J/K, andis the absolute or Kelvin temperature, measured from absolute zero (so that the freezing point of water is273K). The approximate temperature required for the fusion reaction to proceed is very high. This high temperature, required because of the electric repulsion barrier to the reaction, is the main reason why it has been so difficult to make progress toward thermonuclear power generation. Sufficiently high temperatures are found in the interior of the Sun, where fusion reactions take place.

See all solutions

Recommended explanations on Physics Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free