91Ó°ÊÓ

A car moves with an initial velocity of \(18 \mathrm{~m} / \mathrm{s}\) due north. Find the velocity of the car after \(7.0 \mathrm{~s}\) if (a) its acceleration is \(1.5 \mathrm{~m} / \mathrm{s}^{2}\) due north and (b) its acceleration is \(1.5 \mathrm{~m} / \mathrm{s}^{2}\) due south.

Calculate A car moves with an initial velocity of \(18 \mathrm{~m} / \mathrm{s}\) due north. Find the velocity of the car after \(7.0 \mathrm{~s}\) if (a) its acceleration is \(1.5 \mathrm{~m} / \mathrm{s}^{2}\) due north and (b) its acceleration is \(1.5 \mathrm{~m} / \mathrm{s}^{2}\) due south.

Challenge An object has an average acceleration of \(+6.24 \mathrm{~m} / \mathrm{s}^{2}\) for \(0.300 \mathrm{~s}\). At the end of this time the object's velocity is \(+9.31 \mathrm{~m} / \mathrm{s}\). What was the object's initial velocity?

An object has an average acceleration of \(+6.24 \mathrm{~m} / \mathrm{s}^{2}\) for \(0.300 \mathrm{~s}\). At the end of this time the object's velocity is \(+9.31 \mathrm{~m} / \mathrm{s}\). What was the object's initial velocity?

The velocity-time equation for a golf cart is $$ v_{\mathrm{f}}=(1 \mathrm{~m} / \mathrm{s})+\left(-0.5 \mathrm{~m} / \mathrm{s}^{2}\right) t $$ (a) What is the cart's initial velocity? (b) What is the cart's acceleration?

Concept Check The velocity-time equation for a golf cart is $$ v_{\mathrm{f}}=(1 \mathrm{~m} / \mathrm{s})+\left(-0.5 \mathrm{~m} / \mathrm{s}^{2}\right) t $$ (a) What is the cart's initial velocity? (b) What is the cart's acceleration?

An eagle flies with an initial velocity of \(5.0 \mathrm{~m} / \mathrm{s}\) and has a constant acceleration of \(1.3 \mathrm{~m} / \mathrm{s}^{2}\). What is the velocity of the eagle at \(t=2.0 \mathrm{~s}\) ?

Rank Three objects have velocities that vary with time. $$ \begin{array}{|c|l|} \hline \text { Object } & \text { Velocity } \\ \hline 1 & v=2 \mathrm{~m} / \mathrm{s}+\left(3 \mathrm{~m} / \mathrm{s}^{2}\right) t \\ \hline 2 & v=-8 \mathrm{~m} / \mathrm{s}-\left(4 \mathrm{~m} / \mathrm{s}^{2}\right) t \\ \hline 3 & v=1 \mathrm{~m} / \mathrm{s}-\left(5 \mathrm{~m} / \mathrm{s}^{2}\right) t \\ \hline \end{array} $$ (a) Rank the velocities of the three objects at \(t=3 \mathrm{~s}\), from most negative to most positive. Indicate ties where appropriate. (b) Rank the speeds of the three objects at \(t=3 \mathrm{~s}\), from smallest to largest. Indicate ties where appropriate.

A motor scooter is stopped at a traffic light. When the light turns green, the scooter accelerates at \(4.2 \mathrm{~m} / \mathrm{s}^{2}\). (a) How fast is the scooter moving after \(3.0 \mathrm{~s}\) ? (b) How far does the scooter travel in this time?

A soccer ball accelerates from rest and rolls \(6.5 \mathrm{~m}\) down a hill in \(3.1 \mathrm{~s}\). It then bumps into a tree. What is the speed of the ball just before it hits the tree?