Physics 103: Physics for Life Sciences I
County Fair
At a county fair, you try the ring the bell to get a cute stuff
narwhal. You swing the mallet hard enough to give the
ball of mass 50g an initial upward speed of 8 m/s.
1) How much force would I have to apply if the mallet
collapses the lever arm 2 cm?
2) What is the initial kinetic energy of the ball?
3) What is the work done by gravity for the ball to ascend to the bell 3 meters
from the ground?
4) Will the ball hit the bell? Explain using the Work-Kinetic Energy Theorem.
Based on problem from Knight, Jones, and Fields “College Physics” textbook
Physics 103: Physics for Life
Sciences I
Energy – Tennis Ball Testing
Name________________________________
A tennis ball bouncing on a hard surface compresses and then rebounds. The details of
the rebound are specified in tennis regulations. Tennis balls, to be acceptable for
tournament play, must have a mass of 57.5g. When dropped from a height of 2.5 m onto
a concrete surface, a ball must rebound to a height of 1.4 m. During impact, the ball
compresses by approximately 6 mm.
(a) How fast is the ball moving when it hits the concrete surface?
(b) If the ball accelerates uniformly when it hits the floor, what is its approximate
acceleration as it comes to rest before rebounding?
(c) The ball’s kinetic energy just after the bounce is less than just before the bounce. In
what form does this lost energy end up?
(d) By what percent does the kinetic energy decrease?
(e) When a tennis ball bounces from a racket, the ball loses approximately 30% of its
kinetic energy to thermal energy. A ball that hits a racket at a speed of 10 m/s will
rebound with approximately what speed?
Based on problem from Knight, Jones, and Fields “College Physics” textbook
Physics 103: Physics for Life Sciences I
Archimedes Principle
Name_____________________________________
Legend has it that Archimedes was asked by King Hiero of Syracuse to determine
whether a crown was of pure gold or had been adultered with a lesser material by an
unscrupulous goldsmith. It was this problem that led him to the principle that bears his
name. In a modern version of his method, a crown weighing 8.3 N is suspended under
water from a string. The tension in the string is measured to be 7.81 N. Is the crown pure
gold?
(a) Using balance of forces, determine the buoyant force on the crown in water.
(b) Using Archimedes principle, calculate the density of the crown in the problem. The
density of water is 1000 kg/m3 and gold is 17000 kg/m3.
Based on problem from Knight, Jones, and Fields “College Physics” textbook