Describe
Ch 4
Describe
Ch 5
4

What is the difference between average and instantaneous speed? Explain and provide examples.

Average speed is the total distance in meters(m) traveled divided by the time it took to travel that distance in seconds(s). Instantaneous speed is the speed at a specific time, for example if a car is drives 100m in 10s then the car's average speed = 10m/s but say the car is stopped at a red light at 50m, the car's instantaneous speed at that specific time would be 0m/s.

4

Two baseball players are having a race from home plate to second base, both starting at home plate and running in the opposite direction (one rounds third and the other rounds first). One player is 190 lbs and reaches second base in 7 seconds. The other player has the same momentum, but weighs 5 lbs more than the other runner. Which player will reach second base first? (Distance from home to second base is 180’). 1 ft = 0.305 m. 1 lb = 0.454 kg.

Player 1

190 lbs x .454=86.26 kg

Velocity= 54.864 m/7 s= 7.84 m/s

M= 86.26x7.84= 676.28 kg x m/s


Player 2 

676.28 kg x m/s= 88.53 kg x (54.864/change in time)

195 lbs x .454=88.53 kg

676.28/88.53=7.64 m/s

54.864/7.64= 7.18 s


Player 1, being lighter, maintains a slightly higher velocity and arrives first.

4

What are the three key factors in linear motion of a projectile and how it manipulates projectile motion? Explain and provide examples.

  1. Angle of release, speed of release, and height of release. 

  2. The angle of which the object is projected in the air affects its projectile motion, for example, a pitcher throwing a baseball straight up vs pitching a ball too low where distance dominates over height. The faster the speed of release the further or higher the object will travel, for example, if an athlete has a higher take off speed they will jump higher up. As for height of release, height of release influences the flight relative to the surface on which it lands, like a golfer hitting the ball from ground level to green, which is most likely on another level.

4

There is a 120 lb woman on Earth and a 270 lb man on Mars. Which individual is experiencing more force? (Earth- g= -9.81 m/s² & Mars- g= -3.72 m/s²). 1 lb = 0.454 kg.

120 lb x 0.454 kg = 54.48 kg

F=ma

F= 54.48 kg x -9.81 m/s²

F= -534.4488 N


270 lb x 0.454 kg = 122.58 kg

F= ma

F= 122.58 kg x -3.72 m/s²

F= -455.9976 N


The 120 lb woman on Earth is experiencing more force.

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