1. a bullet shot straight up returns to its strarting point in 10second. it init

Question

1. a bullet shot straight up returns to its strarting point in 10second. it inital speed was?

2. a car starting from rest moves with constant acceleration of 2m/s2 for 10s, then travels with constant speed for another 10s, and then finally slows to a stop with constant accleration of -2m/s2. how far does it travel?

3.A motorist travels 160km @ 80km/h and 160km @ 100km/h. what is the average speed of the motorist for this trip?

4.johnny throws a shotput at an angle of 45degrees, and it travels a horizontal distance of 30. meters. If he releases the shotput at the same speed but changes the angle to 55degrees, waht will be the new range (distance)?

Explanation / Answer

1. a bullet shot straight up returns to its strarting point in 10second. it inital speed was? The time of flight T = 2 u / g ==> u = T g / 2 = 10 * 9.8 / 2 = 49 m/s 2. a car starting from rest moves with constant acceleration of 2m/s2 for 10s, then travels with constant speed for another 10s, and then finally slows to a stop with constant accleration of -2m/s2. how far does it travel? The car moved in first 10s is d1 = 0.5 a t^2 = 0.5 * 2.0 * 100 = 100 m The speed of the car at the end of first 10 s is v = a t = 2.0 * 10 = 20 m/s The distance traveled in next 10 second is d2 = v * t = 20 * 10 = 200 m The distance traveled during constant acceleration is - v^2 = 2 a d3 ==> d3 =- v^2 / 2 a = -20^2 / 2 * -2.0 = 100 m The total distance traveled is d = d1 + d2 + d3 = 100 + 200 + 100 = 400 m

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