`\color{fuchsia} ★ \color{fuchsia} ul{\mathbf( "Average Acceleration")} `
The average acceleration `bara` of an object for a time interval Δt moving in x-y plane is the change in velocity divided by the time interval :
`color(blue)(bara=(Deltavecv)/(Deltat))=(Deltav_xhati+Deltav_yhatj)/(Deltat)=(Deltav_x)/(Deltat)hati+(Deltav_y)/(Deltat)hatj`
`color(red)(bara=a_xhati+a_yhatj)`
`\color{fuchsia} ★ \color{fuchsia} ul{\mathbf( "Instantaneous Acceleration")} `
The acceleration (instantaneous acceleration) is the limiting value of the average acceleration as the time interval approaches zero :
`color(blue)(veca=lim_(Deltat->0) (Deltavecv)/(Deltat))`
Since `Δvecv = Δv_xhati + Δv_yhati`, we have
`veca=hati lim_(Deltat->0)[(Deltav_x)/(Deltat)] + hatj lim_(Deltat->0)[(Deltav_y)/(Deltat)]`
`veca=a_xhati+a_yhatj`
where `a_x=(dv_x)/(dt), a_y=(dv_y)/(dt)`
As in the case of velocity, we can understand graphically the limiting process used in defining acceleration on a graph showing the path of the object’s motion. This is shown in `color(red)("Figs. (a) to (d).")`
`P` represents the position of the object at time t and `P_1, P_2, P_3` positions after time `Δt_1, Δt_2, Δt_3`, respectively (`Δt_1 > Δt_2 > Δt_3`). The velocity vectors at points `P, P_1, P_2, P_3` are also shown in Figs. (a), (b) and (c). In each case of Δt, Δv is obtained using the triangle law of vector addition. By definition, the direction of average acceleration is the same as that of `Δv.` We see that as `Δt` decreases, the direction of `Δv` changes and consequently, the direction of the acceleration changes. Finally, in the limit `Δt->0` Fig. (d), the average acceleration becomes the instantaneous acceleration and has the direction as shown.
`\color{green} ✍️ \color{green} \mathbf(KEY \ CONCEPT)`
Note that in one dimension, the velocity and the acceleration of an object are always along the same straight line (either in the same direction or in the opposite direction). However, for motion in two or three dimensions, velocity and acceleration vectors may have any angle between `0°` and `180°` between them.
`\color{fuchsia} ★ \color{fuchsia} ul{\mathbf( "Average Acceleration")} `
The average acceleration `bara` of an object for a time interval Δt moving in x-y plane is the change in velocity divided by the time interval :
`color(blue)(bara=(Deltavecv)/(Deltat))=(Deltav_xhati+Deltav_yhatj)/(Deltat)=(Deltav_x)/(Deltat)hati+(Deltav_y)/(Deltat)hatj`
`color(red)(bara=a_xhati+a_yhatj)`
`\color{fuchsia} ★ \color{fuchsia} ul{\mathbf( "Instantaneous Acceleration")} `
The acceleration (instantaneous acceleration) is the limiting value of the average acceleration as the time interval approaches zero :
`color(blue)(veca=lim_(Deltat->0) (Deltavecv)/(Deltat))`
Since `Δvecv = Δv_xhati + Δv_yhati`, we have
`veca=hati lim_(Deltat->0)[(Deltav_x)/(Deltat)] + hatj lim_(Deltat->0)[(Deltav_y)/(Deltat)]`
`veca=a_xhati+a_yhatj`
where `a_x=(dv_x)/(dt), a_y=(dv_y)/(dt)`
As in the case of velocity, we can understand graphically the limiting process used in defining acceleration on a graph showing the path of the object’s motion. This is shown in `color(red)("Figs. (a) to (d).")`
`P` represents the position of the object at time t and `P_1, P_2, P_3` positions after time `Δt_1, Δt_2, Δt_3`, respectively (`Δt_1 > Δt_2 > Δt_3`). The velocity vectors at points `P, P_1, P_2, P_3` are also shown in Figs. (a), (b) and (c). In each case of Δt, Δv is obtained using the triangle law of vector addition. By definition, the direction of average acceleration is the same as that of `Δv.` We see that as `Δt` decreases, the direction of `Δv` changes and consequently, the direction of the acceleration changes. Finally, in the limit `Δt->0` Fig. (d), the average acceleration becomes the instantaneous acceleration and has the direction as shown.
`\color{green} ✍️ \color{green} \mathbf(KEY \ CONCEPT)`
Note that in one dimension, the velocity and the acceleration of an object are always along the same straight line (either in the same direction or in the opposite direction). However, for motion in two or three dimensions, velocity and acceleration vectors may have any angle between `0°` and `180°` between them.