Average Acceleration The average acceleration a during the time interval At, is defined as the change in velocity Av divided by the△t △t It is a vector Physics 121: Lecture 4, Pg 6
Physics 121: Lecture 4, Pg 6 Average Acceleration The average acceleration a during the time interval t, is defined as the change in velocity v divided by the t It is a vector … f i f i t t v v t v a − − = =
Instantaneous Acceleration The instantaneous acceleration a is defined as the limit of the average acceleration as the time interva△ t goes to zero m av A→>0△t Physics 121: Lecture 4, Pg 7
Physics 121: Lecture 4, Pg 7 Instantaneous Acceleration The instantaneous acceleration a is defined as the limit of the average acceleration as the time interval t goes to zero t v a t →0 lim
Kinematic variables Measured with respect to a reference frame (X-y axis) Measured using coordinates(having units) Many kinematic variables are vectors, which means they have a direction as well as a magnitude Vectors denoted by boldface v or arrow v Physics 121: Lecture 4, Pg 9
Physics 121: Lecture 4, Pg 9 Kinematic Variables Measured with respect to a reference frame. (x-y axis) Measured using coordinates (having units). Many kinematic variables are vectors, which means they have a direction as well as a magnitude. Vectors denoted by boldface v or arrow v
Newton's 2nd law and acceleration It relates the net force to the acceleration net一 ∑码 ma A force is what changes the velocity of a particle No net force: no change in velocity The constant of proportionality is the mass For a given Fnet a more massive object will undergo a smaller acceleration (and vice versa) Physics 121: Lecture 4, Pg 10
Physics 121: Lecture 4, Pg 10 Newton’s 2nd law and acceleration It relates the net force to the acceleration A force is what changes the velocity of a particle No net force: no change in velocity The constant of proportionality is the mass For a given Fnet a more massive object will undergo a smaller acceleration (and vice versa)
Motion in 1 dimension In 1-D, we usually write position as X Since it's in 1-D. all we need to indicate direction is or Displacement in a time△t=t+-tis△X=x-X; X some particle's trajectory △X in 1-D △t Physics 121: Lecture 4, Pg 11
Physics 121: Lecture 4, Pg 11 Motion in 1 dimension In 1-D, we usually write position as x . Since it’s in 1-D, all we need to indicate direction is + or −. Displacement in a time t = tf - t i is x = xf - xi t x t i t f x t xi xf some particle’s trajectory in 1-D