Chapter N4

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Chapter N4 - PowerPoint PPT Presentation

Chapter N4. Motion from forces Due Friday: N4.B1, B2, B.7, B.8. These are graphs showing the motion of a car along a straight road. Explain what is happening to the displacement, the velocity and the acceleration of the car. r. v. a. t. Problems.

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Chapter N4

Motion from forces

Due Friday: N4.B1, B2, B.7, B.8

These are graphs showing the motion of a car along a straight road. Explain what is happening to the displacement, the velocity and the acceleration of the car.

r

v

a

t

Problems
• Case 1. An object is thrown straight into the air and falls back. t=0 when the object leaves the hand which happens at y = 0. Draw the curve until the object comes back to the starting point.
• Case 2. A rocket is shot straight in the air with an engine that burns for 4 seconds. It then falls back to earth.

Similar equations exist for y, and z.

Use the x, y, or z equations depending on the direction of the force (acceleration).

Often this will be the vertical direction and the acceleration will be g.

Sample problem: A car starts from rest and accelerates (2m/s2)for 5 seconds. What are the velocity and position of the car at that time?

• List the data on your paper, raise your hand when you are done. 6
• x0=0, v0=0, a=2 m/s2, t = 5 sec, v = ?, x = ?.

v=10m/s

x=25m

An object is dropped starting from rest from a height of 25 m. Find the position and velocity of the object at the end of 2.2 s.
• Write the data. Raise your hand when done.
• y0=25 m, v0=0, a = -9.8 m/s2, t = 2.2 s, v = ?, y = ?

v = - 9.6 m/s

y = 23.7 m

How long will it take the ball to strike the ground?

t = 2.26 s

An object thrown straight up from a height of 25 m with a velocity of 12 m/s. Find the position and velocity of the object at the end of 2.2 s.

• Write the data. Raise your hand when done.
• y0=25 m, v0=12 m/s, a = -9.8 m/s2, t = 2.2 s, y = ?, vy=?

v = - 9.6 m/s m/s

y = -23.7 + 26.4 + 25 m = 27.7 m

t = 3.8 s

A ball is thrown straight into the air and takes 3 seconds to fall back to the ground.
• What is the maximum height of the ball and with what velocity was it thrown into the air?
• Write the data.
• Write the equation to find the velocity with which it was thrown.
• Find the velocity.
• Write the equation to find the height.
• Find the height.

v = 14.7 m/s

y = 11 m

Problems due Friday
• N4.B1, B2, B.7, B.8