Test Review Chapter 4 – Linear Motion

Question You’re solving a problem and you see a unit of km/hr. What variable is this giving you?

Answer speed

Question The acceleration vector of a moving object points at an angle to the velocity vector. What does this tell us about the motion of the object?

Answer It’s changing direction

Question 15 You get pulled over for going 50 mph in a 35 mph zone. Is this based on your average or instantaneous speed?

Answer instantaneous

Question 16 What is the equation used to calculate the average speed of an object?

Answer Speed = change in distance/change in time

Question 17 A description of how fast something moves is __________.

Answer Speed

Question You are solving a problem and you see the units of m/s². What variable is this giving you?

Answer acceleration

Question 18 A description of how fast and in what direction something moves is _________.

Answer Velocity

Question A ball is thrown upward with a speed of 50 m/s. If it is caught at the same height where it was released, how fast is it traveling?

Answer 50 m/s

Question 19 What are 3 ways an object can undergo an acceleration?

Answer Speed up, slow down, change direction

Question 20 What is the equation used to calculate an object’s acceleration?

Answer Acceleration = change in speed/change in time

Question On the turnpike, they are trying to pass a law that based on what time you pass through each toll booth, you may get a speeding ticket in the mail. Is this based off average speed or instantaneous speed?

Answer Average

Question 21 What are the standard SI units of acceleration?

Answer m/s²

Question What physical quantity does “g” represent?

Answer Acceleration due to gravity

Question 22 True or False: the acceleration of an object undergoing free fall motion is constant.

Answer True

Question 23 In each passing second, how does the speed of an falling object change?

Answer It increases by 10 m/s

Question24 What is the equation used to determine how far an object undergoing free fall motion has fallen from a specific zero reference point?

Answer d = ½ gt²

Question 25 Why can you not use d=vt to solve for distance in cases involving free fall motion?

Answer In order to use d=vt, there must be NO acceleration (in other words the speed must be constant). Clearly in free fall motion, the object is accelerating towards Earth.

Question A ball is allowed to rise and fall under free fall motion. What is its acceleration at the highest point?

Answer 10 m/s²

Question 26 For each second of free fall motion, how does the distance fallen compare with that of the previous time interval?

Answer It is greater. This is because the object is accelerating and therefore its speed is increasing constantly and therefore covering more and more distance.

Question 27 A linear graph of distance vs time shows that the object’s ___________ is constant.

Answer Speed, the slope of a distance vs. time graph gives speed. If the slope is constant ( in other words linear) then the speed is constant.

Question Sketch what the distance vs time graph of a freely falling object would look like?

Answer parabolic

Question A ball is allowed to rise and fall under free fall motion. What is its speed at its highest point?

Answer O m/s

Question 28 A linear graph of speed vs. time shows that the object’s __________ is constant.

Answer Acceleration. The slope of a speed vs. time graph gives acceleration. If the slope is constant ( in other words linear) then the acceleration must be constant.

Question 29 In a distance vs. time graph, the steepness of the slope continues to increase as time passes. What does this mean?

Answer Speed increases and object is accelerating. Speed is given by the slope of a distance vs. time graph so steeper slopes correspond to greater speeds. If speed is increasing then object is accelerating.

Question 30 What is the difference between average speed and instantaneous speed?

Answer Average speed is how fast you have to constantly travel in order to cover a given distance in a given time. Instantaneous speed is the speed of an object at a particular moment in time.

Question 31 Calculate the speed of a bowling ball that moves 8 meters in 4 seconds.

Answer 2 m/s

Question Sketch what the speed vs. time graph of an object undergoing free fall motion would look like.

Answer linear

Question For a moving object, the acceleration vector points in the opposite direction of the velocity vector. What does this tell us about the motion of the object?

Answer It’s slowing down

Question 32 Calculate the distance Charlie runs if he maintains an average speed of 10 m/s for 40 seconds.

Answer 400 m

Question 33 Calculate the acceleration of a ball that starts from rest and rolls down a ramp and gains a speed of 25 m/s in 5 seconds.

Answer 5 m/s²

Question 34 Calculate the speed (in m/s) of a skateboarder who accelerates from rest for 3 seconds down a ramp at an acceleration of 5 m/s²

Answer 15 m/s

Question 35 A sky diver steps from a high-flying helicopter. If there were no air resistance, how fast would she be falling at the end of a 12 second jump?

Answer 120 m/s

Question 36 An apple drops from a tree and hits the ground in 1.5 s. Calculate how far it falls.

Answer 11.3 m

Question 37 On a distant planet a freely falling object has an acceleration of 20 m/s². Calculate the speed an object dropped from rest on this distant planet acquires in 1.5 s.

Answer 30 m/s

Question A ball is thrown downward with a speed of 14 m/s. Upon impact with the ground, the balling is traveling at a speed of 30 m/s. How high was the ball when it was thrown?

Answer 35.2 m

Question A basketball player goes to shoot a layup. If he leaves the ground with a speed of 17 m/s, how long is he in the air for?

Answer 3.4 s