A particle $$$P$$$ moves in a straight line. It starts at a point $$$O$$$ on the line and at time $$$t$$$ s after leaving $$$O$$$ it has velocity $$$v \mathrm{~m} \mathrm{~s}^{-1}$$$, where $$$v=4 t^{2}-20 t+21$$$. Find the values of $$$t$$$ for which $$$P$$$ is at instantaneous rest. ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................

Mathematics

IGCSE&ALevel

CAIE

Exam No：9709_w20_qp_43 Year：2020 Question No：5(a)

Answer:

$4 t^{2}-20 t+21=(2 t-3)(2 t-7)=0 \rightarrow t=\ldots$
$t=1.5$ and $t=3.5$

Knowledge points:

4.2.1 understand the concepts of distance and speed as scalar quantities, and of displacement, velocity and acceleration as vector quantities Restricted to motion in one dimension only. The term ‘deceleration’ may sometimes be used in the context of decreasing speed.

Answer:

Knowledge points:

Solution:

Related Question