An object moves along the x axis according to the equation x = 3.75t - 2.00t + 3.00, where x is in meters and t is in seconds. (a) Determine the average speed between t = 1.80 s and t = 3.50 s. 14.5 x The average speed is the distance traveled divided by the time. Is the distance traveled equal to the displacement in this case? m/s (b) Determine the instantaneous speed at t = 1.80 s. 8.26 We are given an explicit expression for x as a function of time. Calculus methods can be used to determine the velocity as a function of time, m/s Determine the instantaneous speed at t = 3.50 s. 18 X We are given an explicit expression for x as a function of time. Calculus methods can be used to determine the velocity as a function of time, m/'s (c) Determine the average acceleration between t = 1.80 s and t = 3.50 s. 5.7 X You appear to have correctly calculated the acceleration using your incorrect values from part (b). m/s (d) Determine the instantaneous acceleration at t = 1.80 s. 5.7 X The instantaneous acceleration is equal to the average acceleration in this case, but your value for the average acceleration is incorrect. m/s Determine the instantaneous acceleration at + = 3.50 s. 5.7 X The instantaneous acceleration is equal to the average acceleration in this case, but your value for the average acceleration is incorrect. m/s (e) At what time is the object at rest? 0.35 X The instantaneous velocity will be zero when the object is at rest. Take the derivative of x (t) to find v(t). s9. [0/1.33 Points] DETAILS PREVIOUS ANSWERS SERPSE9 2.P.072. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER A catapult launches a test rocket vertically upward from a well, giving the rocket an initial speed of 79.6 m/'s at ground level. The engines then fire, and the rocket accelerates upward at 4.20 m/'s" until it reaches an altitude of 1160 m. At that point its engines fail, and the rocket goes into free fall, with an acceleration of -9.80 m/s". (You will need to consider the motion while the engine is operating and the free-fall motion separately.) (a) For what time interval is the rocket in motion above the ground? 1X s b) What is its maximum altitude? x km (c) What is its velocity just before it hits the ground? x m/s Additional Materials eBook 10. [0/1.33 Points] DETAILS PREVIOUS ANSWERS MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER A car is moving too fast at a constant speed of 32.7m/s. Law enforcement observes the fast moving car. The law enforcement officer starts from rest just as the fast moving car passes it, and accelerates at a constant rate of 2.1m/s . The maximum speed of the police car is 49.8m/'s. When the officer's vehicle reaches maximum speed, it moves at a constant speed. a. How long does the law enforcement take to catch the speeder?| X s b. What distance has each car traveled? x m 11. [0/1.33 Points] DETAILS PREVIOUS ANSWERS SERPSE9 2.P.079.SOLN. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER Liz rushes down onto a subway platform to find her train already departing. She stops and watches the cars go by. Each car is 8.60 m long. The first moves past her in 1.40 s and the second in 1.17 s. Find the constant acceleration of the train. x m/s2 Additional Materials eBook12. [0/1.33 Points] DETAILS PREVIOUS ANSWERS MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER Last week John Oliver trained for a 100m race. John decided to use his knowledge of kinematics to analyze last week's practice. Film analysis showed that John Oliver started at rest and then accelerated to a maximum speed at a constant acceleration for the first 3s, and finished in 10.37s. a. What values did John Oliver get for his acceleration and maximum speed? X m/s * m/'s b. John Oliver wants to approximate the time to run a 200m dash. Assuming the same acceleration and maximum speed as above, determine the time required to complete the race. * s 13. [0/1.33 Points] DETAILS PREVIOUS ANSWERS SERPSE9 2.P.073.MI. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER Kathy tests her new sports car by racing with Stan, an experienced racer. Both start from rest, but Kathy leaves the starting line 1.00 s after Stan does. Stan moves with a constant acceleration of 3.4 m/'s" while Kathy maintains an acceleration of 5.27 m/s". (a) Find the time at which Kathy overtakes Stan. x s from the time Kathy started driving (b) Find the distance she travels before she catches him. x m (c) Find the speeds of both cars at the instant she overtakes him. Kathy x m/s Stan x m/s Need Help? Master It Additional Materials LO eBook 14. [0/1.33 Points] DETAILS PREVIOUS ANSWERS MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER It is late at night and your are on the road in your SUV on Interstate 80. You are moving at a speed of 18.2m/s. Suddenly you see a large animal in the road 37.6 m ahead. a. Given that you can reduce your speed at a maximum rate of 4.60 m/'s", what reaction time is needed to avoid plowing into the animal? X s b. Suppose your reaction time is about 0.3s, how fast will you be traveling when you plow into the poor moose? 1 x m/s