Question

 A car whose initial speed is 30 m/s slows uniformly to 10 m/s in 5 seconds. Determine the acceleration of the car. Sketch a graph to support your answer. CHALLENGE: Determine the distance it travels in the 3 seconds.
This one is a little harder because you have to make a graph :(

Answer 1

• Initial velocity=u=30m/s
• Final velocity=v=10m/s
• Time=5s

$\\ \sf\longmapsto Acceleration=\dfrac{v-u}{t}$

$\\ \sf\longmapsto Acceleration=\dfrac{10-30}{5}$

$\\ \sf\longmapsto Acceleration=\dfrac{-20}{5}$

$\\ \sf\longmapsto Acceleration=-4m/s^2$

Now

For the second question

• Time=3s

Using 2nd equation of motion

$\\ \sf\longmapsto s=ut+\dfrac{1}{2}at^2$

$\\ \sf\longmapsto s=30(3)+\dfrac{1}{2}(-4)(3)^2$

$\\ \sf\longmapsto s=90-2(9)$

$\\ \sf\longmapsto s=90-18$

$\\ \sf\longmapsto s=72m$