# Kinematics.

## Presentation on theme: "Kinematics."— Presentation transcript:

Kinematics

Problem-Solving Strategy
Visualize Draw a pictorial representation. Label all the objects that are involved in the situation. Draw a physical representation (i.e origin, axis, vectors) Restate the question. What are you trying to find? Solve Now translate physical into a mathematical representation What is the physics equation(s) that you are going to use? State what you are solving for. Assess Is your result believable? Does it make sense? Does it have the proper units? Is your solution complete?

Clickers This will NEVER be used for marks
Clickers are a tool to help ME to know what we need to spend more time on And for YOU to get more participate (i.e. Be more of a active learner) So don’t cheat because you would be cheating yourself.

An object goes from one point in space to another.
After it arrives at its destination, its displacement is _________________ than the distance it traveled. 1. either greater than or equal to 2. always greater than 3. always equal to 4. either smaller than or equal to 5. always smaller than 6. either smaller or larger Answer: 4.The displacement is the vector pointing from the final and to the initial position (and can be negative).The distance traveled is the absolute length of the path traversed; it is always positive and can be larger than the displacement.

What is the maximum and minimum magnitude a resulting can have if one vector has a magnitude of 10cm and another 5cm? 15cm and 5cm -15cm and 15cm 10cm and 5cm 10cm and -5cm This is great question to help students learn ways to assess if there solution is reasonible

1. Which position-versus-time graph represents the motion shown in the motion diagram?

2. Which of velocity-versus-time graph goes with the position-versus-time graph on the left?
d Answers is c slope of the d-t graph=speed

3. Which of the position-versus-time graph goes with the velocity-versus-time graph on the left?
Answers is b recall that, speed = slope of the line of the position-versus-time. Now let start talking about non uniform motion

4. Which of the velocity-versus-time graphs goes with this acceleration-versus-time graph? The object is initially moving in the negative direction.

Which of the following motions is best described by the velocity-time graph below? A) A marble rolling up a hill and down the other side. B) A car speeding up on a road, and braking to a stop. C) A Loonie coin is thrown up and falls down. D) A horse runs one lap around a circular track. E) A basketball is dropped and bounces back up. Answer: B

If you drop an object in the absence of air resistance, it accelerates downward at 9.8 m/s2. If instead you throw it downward, its downward acceleration after release is 1. less than 9.8 m/s2. m/s2. 3. more than 9.8 m/s2. Answer: 2.The acceleration of gravity is a constant, independent of initial velocity.

A marathon runner runs at a steady 15 km/hr. When the runner is 7
A marathon runner runs at a steady 15 km/hr. When the runner is 7.5 km from the finish, a bird begins flying from the runner to the finish at 30 km/hr. When the bird reaches the finish line, it turns around and flies back to the runner, and then turns around again, repeating the back-and-forth trips until the runner reaches the finish line. How many kilometers does the bird travel? 1. 10 km 2. 15 km 3. 20 km 4. 30 km Answer: 2. It takes the runner half an hour to reach the finish.

3. neither—they both hit at the same speed.
A person standing at the edge of a cliff throws one ball straight up and another ball straight down at the same initial speed. Neglecting air resistance, the ball to hit the ground below the cliff with the greater speed is the one initially thrown 1. upward. 2. downward. 3. neither—they both hit at the same speed. Answer: 3. Upon its descent, the velocity of an object thrown straight up with an initial velocity v is exactly –v when it passes the point at which it was first released.

A stone of mass M thrown straight up with initial velocity v1 reaches a height H. A second stone of mass 2M, thrown straight up with an initial velocity 2v1 will reach a height A) H/2 B) H C) √2H D) 2H E) 4H Answer: E

1. At time tB, both trains have the same velocity.
The graph shows position as a function of time for two trains running on parallel tracks. Which is true? 1. At time tB, both trains have the same velocity. 2. Both trains speed up all the time. 3. Both trains have the same velocity at some time before tB. 4. Somewhere on the graph, both trains have the same acceleration. Answer: 3.The slope of curve B is parallel to line A at some point t < tB.

3. speeds up part of the time and slows down part of the time.
A train car moves along a long straight track. The graph shows the position as a function of time for this train. The graph shows that the train: 1. speeds up all the time. 2. slows down all the time. 3. speeds up part of the time and slows down part of the time. 4. moves at a constant velocity. Answer: 2.The slope of the curve diminishes as time increases.

A graph of acceleration in m/s2 versus time in s is shown
A graph of acceleration in m/s2 versus time in s is shown. The change in velocity of this object from t = 0 s to t = 10 s is closest to A) 40 m/s. B) -40 m/s. C) 80 m/s. D) –80 m/s. E) 0 m/s. 8 a(m/s2) Answer: A 10 t(s)

A bottle dropped from a balcony strikes the sidewalk below with a particular speed. In order for the bottle to strike with double that speed, the bottle must be dropped from a height that is A) 1.4 times higher B) twice as high C) three times as high D) four times as high E) eight times as high Answer: D

Two trains are 1.0 km long. Train X moves at 45 km/h [E] while Train Y moves at 30 km/h [W] on a parallel track. How much time elapses from the moment the two locomotives meet, until the two cabooses are just separating? A) 240 s B) 160 s C) 120 s D) 96 s E) 80 s Answer: D

A race car starts from rest and accelerates at a constant rate a
A race car starts from rest and accelerates at a constant rate a. It covers a distance d in a time t. How long would it take to cover an additional distance 8d at the same acceleration? A) B) C) D) E)

You are throwing a ball straight up in the air.
At the highest point, the ball’s 1. velocity and acceleration are zero. 2. velocity is nonzero but its acceleration is zero. 3. acceleration is nonzero, but its velocity is zero. 4. velocity and acceleration are both nonzero. Answer: 3.The ball reaches its highest point when its velocity is zero; the acceleration of gravity is never zero.

A battleship simultaneously fires two shells at enemy ships
A battleship simultaneously fires two shells at enemy ships. If the shells follow the parabolic trajectories shown, which ship gets hit first? 1. A 2. both at the same time 3. B 4. need more information Answer: 3. The time a projectile spends in the air is equal to twice the time it takes to fall from its maximum height. Because the shell fired at ship A reaches a higher altitude than the one aimed at B, the former takes longer to return to sea level.