PHY 1200 – Foundation Physics
Worksheet 3
1. Joe Ponder, from North Carolina, once used his teeth to lift a pumpkin with a mass of 275 kg.
Suppose Ponder has a mass of 75 kg, and he stands with each foot on a platform and lifts the
pumpkin with an attached rope. If he holds the pumpkin above the ground between the
platforms, what is the force exerted on his feet?
2. David Purley, a racing driver, survived deceleration from 173 km/h to 0 km/h over a distance
of 0.660 m when his car crashed. Assume that Purley’s mass is 70.0 kg. What is the average
force acting on him during the crash? Compare this force to Purley’s weight. (Hint: Calculate
the average acceleration first.)
3. Lake Point Tower in Chicago is the tallest apartment building in the United States (although
not the tallest building in which there are apartments). Suppose you take the elevator from
street level to the roof of the building. The elevator moves almost the entire distance at
constant speed, so that it does
1.15  10 5 J of work on you as it lifts the entire distance. If your mass is
60.0 kg, how tall is the building? Ignore the effects of friction.
4. In 1994, Leroy Burrell of the United States set what was then a new world record for the men’s
100 m run. He ran the 1.00  102 m distance in 9.85 s. Assuming that he ran with a constant
speed equal to his average speed, and his kinetic energy was 3.40  103 J, what was Burrell’s
mass?
5. The tops of the towers of the Golden Gate Bridge, in San Francisco, are 227 m above the water.
Suppose a worker drops a 655 g wrench from the top of a tower. If the average force of air
resistance is 2.20 percent of the force of free fall, what will the kinetic energy of the wrench be
when it hits the water?
6. In 1987, Stefka Kostadinova from Bulgaria set a new women’s record in high jump. It is known
that the ratio of the potential energy associated with Kostadinova at the top of her jump to her
mass was 20.482 m2/s2. What was the height of her record jump?
7. In 1936, Col. Harry Froboess of Switzerland jumped into the ocean from the airship Graf
Hindenburg, which was 1.20  102 m above the water’s surface. Assuming Froboess had a
mass of 72.0 kg, what was his kinetic energy at the moment he was 30.0 m from the water’s
surface? What was his speed at that moment? Neglect the air resistance.
8. Reginald Esuke from Cameroon ran over 3 km down a mountain slope in just 62.25 min. How
much work was done if the power developed during Esuke’s descent was 585.0 W?
9. In 1991, a Swedish company, Kalmar LMV, constructed a forklift truck capable of raising 9.0 
104 kg to a height of about 2 m. Suppose a mass this size is lifted with an upward velocity of 12
cm/s. The mass is initially at rest and reaches its upward speed because of a net force of 6.0 
103 N exerted upward. For how long is this force applied?
10. The largest single publication in the world is the 1112-volume set of British Parliamentary
Papers for 1968 through 1972. The complete set has a mass of 3.3  103 kg. Suppose the entire
publication is placed on a cart that can move without friction. The cart is at rest, and a
librarian is sitting on top of it, just having loaded the last volume. The librarian jumps off the
cart with a horizontal velocity relative to the floor of 2.5 m/s to the right. The cart begins to
roll to the left at a speed of 0.05 m/s. Assuming the cart’s mass is negligible, what is the
librarian’s mass?
11. Zorba, an English mastiff with a mass of 155 kg, jumps forward horizontally at a speed of 6.0
m/s into a boat that is floating at rest. After the jump, the boat and Zorba move with a velocity
of 2.2 m/s forward. Calculate the boat’s mass.
References
Serway, R. A., Faughn, J. S., & McDougal, H. (2012). Holt McDonald Physics. Orlando: Houghton
Mifflin Harcourt Publishing Company