Chapter N4 Motion from forces Due Friday: N4.B1, B2, B.7, B.8
a t v r 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.
Problems for the groups When your group has the curves drawn, draw them on the board. Case 1. An object is shot straight into the air and falls back (like the balls you shot in the air). t=0 v=v 0 when the ball leaves the gun. Draw the curve until the ball comes back to the starting point. Case 2. A rocket is shot straight in the air with an engine that burns for 4 seconds with an acceleration of 20 m/s 2. It then falls back to earth. As soon as you are ready put them on the board. The first group done with both problems gets 5 bonus points. A group that successfully points out problems with another group’s answer receives 2 bonus points.
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.
Equations for your formula sheet 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/s 2 ) 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 x 0 =0, v 0 =0, a=2 m/s 2, 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. y 0 =25 m, v 0 =0, a = -9.8 m/s 2, t = 2.2 s, v = ?, y = ? v = 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. y 0 =25 m, v 0 =12 m/s, a = -9.8 m/s 2, t = 2.2 s, y = ?, v y =? v = m/s m/s y = 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