Motion in One Dimension Section 1

Preview

Section 1 Displacement and Velocity

Section 2 Acceleration

Section 3 Falling Objects

Motion in One Dimension Section 3

Free Fall

• Assumes no air resistance• Acceleration is constant for the entire fall

• Acceleration due to gravity (ag or g )– Has a value of -9.81 m/s2

• Negative for downward

– Roughly equivalent to -22 (mi/h)/s

Motion in One Dimension Section 3

Free Fall

• For a ball tossed upward, make predictions for the sign of the velocity and acceleration to complete the chart.

Velocity

(+, -, or zero)

Acceleration

(+, -, or zero)

When halfway up

When at the peak

When halfway down

+ -

zero -

- -

Motion in One Dimension Section 3

Click below to watch the Visual Concept.

Visual Concept

Free Fall

Motion in One Dimension Section 3

Graphing Free Fall

• Based on your present understanding of free fall, sketch a velocity-time graph for a ball that is tossed upward (assuming no air resistance).– Is it a straight line?– If so, what is the slope?

• Compare your predictions to the graph to the right.

Motion in One Dimension Section 3

Click below to watch the Visual Concept.

Visual Concept

Velocity and Acceleration of an Object at its High Point

Motion in One Dimension Section 3

Classroom Practice Problem

A ball is thrown straight up into the air at an initial velocity of 25.0 m/s upward. Create a table showing the ball’s position, velocity and acceleration each second for the first 5 s.

20.1 +15.2 -9.81 t (s) y (m) v (m/s) a (m/s2)

1.00

2.00

3.00

4.00

5.00

30.4 +5.4 -9.81

30.9 -4.4 -9.81

21.6 -14.2 -9.81

2.50 -24.0 -9.81

Motion in One Dimension Section 3

Practice Problems

• Jason hits a volleyball so that it moves with an initial velocity of 6.0 m/s straight upward. If the volleyball starts from 2.0m above the floor, how long will it be in the air before it strikes the floor?– t= 2.55s

Motion in One Dimension Section 3

Practice Problems

• Jason hits a volleyball so that it moves with an initial velocity of 6.0 m/s straight upward. If the volleyball stats from 2.0m above the floor, how long will it be in the air before it strikes the floor?What is the displacement and velocity of the ball after

0.50s after Jason hits it?– X=1.8 m and +1.1 ms

Motion in One Dimension Section 3

Practice Problems

• Stephanie serves the volleyball from a height of 0.80m and gives it an initial velocity of +7.6 m/s straight up?How high will it go?– X=3.7 m

Motion in One Dimension Section 3

Practice Problems

• Stephanie serves the volleyball from a height of 0.80m and gives it an initial velocity of +7.6 m/s straight up?How long will it take the ball to reach its maximum

height?– t= 0.77 s

Motion in One Dimension Section 3

Practice Problems

• A tennis ball is thrown vertically upward with an initial velocity of +8.0 m/s?What will its speed be when it returns to it’s starting

position?– V= 8.0 m/s

Motion in One Dimension Section 3

Practice Problems

• A tennis ball is thrown vertically upward with an initial velocity of +8.0 m/s?How long will it take for it to reach its starting position?– t= 1.63 s

Motion in One Dimension Section 3

Practice Problems

• A flowerpot falls from a windowsill 25.0 m above the sidewalk?How fast is the flowerpot moving when it strikes the

ground?– V= 22.1 m/s

Motion in One Dimension Section 3

Practice Problems

• A flowerpot falls from a windowsill 25.0 m above the sidewalk?How much time does the passerby on the sidewalk

have to move out of the way before the flowerpot hits the ground?

– t= 2.25 s

Motion in One Dimension Section 3

Practice Problems

• A robot probe drops a camera off the rim of a 24 km deep crater on Mars, where the free fall acceleration is -3.7 m/s2. Find the time it takes for the camera to reach the crater floor and the velocity with which it hits?– t= 110 s and -420 m/s

Motion in One Dimension Section 3

Practice Problems

• Maria throws an apple vertically upward from a height of 1.3 m with an initial velocity of +2.4 m/s.Will the apple reach Maria’s friend in a tree house 5.3 m

above the ground?– No

Motion in One Dimension Section 3

Practice Problems

• Maria throws an apple vertically upward from a height of 1.3 m with an initial velocity of +2.4 m/s.If the apple is not caught, how long will the apple be in

the air before it hits the ground?– 0.82 s