2.7 Beginning from rest, a giraffe accelerates at 0.46 m/s? . a) If the giraffe\
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2.7 Beginning from rest, a giraffe accelerates at 0.46 m/s? . a) If the giraffe's top speed is 14 m's, how long does it take for the giraffe to get to its top speed? b) IHow far does the giraffe go in that amount of time? 2.8 A car is going 7 m's when it begins to accelerate. Sixty meters further down the road, the car is going 24 m/s. a) What was the acceleration of the car? b) How much time did the change from 7 m/s to 24 m/s take? 2.9 A jet plane that has a minimum takeoff speed of 80 m/s begins 70 m from one end of the runway. The runway is 2200 m long. What acceleration must it have to takeoff with 100 m to spare on the other end of the runway? 2.10 A car is going down the road when the driver applies the brakes. Four seconds later, at a point 110 m further down the road, the velocity is 15 m/s, a) What was the initial velocity? b) What was the acceleration? 2.11 As hockey puck slides to a stop, it goes 40 m across the ice in 3.7 s. a) What was the initial velocity of the puck? b) What was the acceleration of the puck? 2.12 Two ice skaters, Frank and Mary, are initially facing each other and separated by 2000 m on a smooth frozen lake. Mary begins skating towards Frank at t 0 s with an acceleration of 0.75 m/s. After she reaches a speed of 12 m/s, she continues skating at a constant 12 m/s. Three seconds after Mary begins to skate, Frank starts skating. He accelerates at 1.1 m/s for 9 s and then skates at a constant speed. a) When do the skaters pass each other? b) How far from Mary's starting position is the point at which the skaters pass each other? 2.13 A rocket sled begins from rest. In the first 3 s, it goes 100 m at a constant acceleration. a) What is the velocity at the end of the first 3 s? b) What was the acceleration? c) If the maximum velocity of the rocket sled is 290 m's, bow long does it take to reach that velocity? d) How far does the rocket sled go in that amount of time? 2.14 A car is going south on 1-69 at 33 m's (74 mph). The car has good brakes so its maximum braking acceleration is -8.5 m's?. Traffic has come to a stop in all lanes 120 m abead a) If the driver reacts in 0.50 s, what acceleration will be needed for the car to stop? Note that during the reaction time, the car continues at 33 m/s. b) If the driver is sending a text message and dosn see the stopped traffic for 2.5 s, can the car stop before running into the stationary vehi this case, the total reaction time is 3 s.) e) If the car cannot stop in time, what is the speed? Convert your final answer into miles per hour. 2.15 A ball is thrown upward with an initial velocity of 25 m/s. a) What is the max reached by the ball? b) How much time does it take for the ball to return to the lExplanation / Answer
here,
2.7)
accelration , a = 0.46 m/s^2
a)
top speed , v = 14 m/s
let the time taken be t
v = u + a * t
14 = 0 + 0.46 * t
solving for t
t = 30.4 s
the time taken is 30.4 s
b)
the distance travelled , s = u * t + 0.5 * a * t^2
s = 0 + 0.5 * 0.46 * 30.4^2 m
s = 213 m
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