The Physics
Hypertextbook
Opus in profectus

# Force and Mass

## Problems

### practice

1. A supertanker doesn't come with brakes. Using engines alone, it takes a loaded supertanker 13 km (8 miles) to stop. A typical vessel of this class has a gross mass of about 150 million kilograms (150 thousand tons) and a cruising speed of 50 kph (30 mph). Determine the average stopping force applied to the ship.
2. Write something completely different.
3. Write something different.
4. Write something completely different.

### conceptual

1. As a rocket rises its acceleration increases. Why does this happen? (Assume that the acceleration due to gravity and air resistance are nearly constant during the ascent.)

### numerical

1. Before a transparent material can be approved for use as a windshield in an airplane, it must first pass the "bird-impact resistance" test. A genuine (dead) or artificial chicken is accelerated to aircraft cruising speeds from the mouth of an air cannon and aimed at the windshield prototype. If the material shows any significant form of damage it fails the test. Each part of this problem contains an except from a USAF News Agency report.
1. "Aircrews… find nothing funny about bird strikes. A strategically placed feathered bullet can wreak the same amount of damage as a laser-guided missile. The impact of a four-pound bird at 500 mph lasts less than a thousandth of a second, but can generate forces exceeding 100,000 pounds." Verify this statement; that is, that show that such a collision would indeed exert the force claimed.
2. "They fire gelatin-molded, artificial birds weighing four pounds apiece, out a compressed air, 30 foot barrel cannon, which can shoot at speeds up to 900 mph. Three lasers and photodetectors measure the artificial chicken's velocity, while three cameras shoot the impact at 6000 frames per second." Calculate the force exerted by the cannon on the chicken.
2. An 11.3 g bullet leaves the muzzle of a 61 cm rifle with a horizontal velocity of 922 m/s. It strikes a target 457 m away with a horizontal velocity of 650 m/s. Determine…
1. the acceleration of the bullet in the rifle
2. the force of the propellant on the bullet in the rifle
3. the horizontal acceleration of the bullet after it left the rifle barrel
4. the aerodynamic drag on the bullet after it left the rifle barrel
5. the time it took the bullet to travel the distance between the muzzle and the target
6. how far the bullet fell by the time it hit the target

### statistical

1. The table below shows some of the best and worst performing cars in an emergency braking test.
Emergency braking test Source: Road & Track, 2010
make
model
weight/mass initial speed braking distance
(lb) (kg) (mph) (m/s) (ft) (m)
Mercedes-Benz
E550 Coupe
3810 1728 80 35.8 252 76.8
Porsche
911 GT3
3075 1395 80 35.8 186 56.7
Volkswagen
Golf GTI 3-dr
3370 1529 60 26.8 143 43.6
Alfa Romeo
8C Competizione
3495 1585 60 26.8 105 32.0
1. For all four cars, determine the…
1. braking acceleration
2. braking force