An object travels North at #7 m/s# for #5 s# and then travels South at #9 m/s# for # 2 s#. What are the object's average speed and velocity?

1 Answer
May 13, 2016

Answer:

#vecV_"net"=2.43m/s->"towards north"#

#V_"avg" ~~7.6m/s #

Explanation:

For 1st 5s the velocity of the object towards North be
#vecV_"north"=7hatjm/s#

For 1st 5s the displacement of the object towards North be
#vecd_"north"=7hatjm/sxx5s=35hatjm#

For 2nd 2s the velocity of the object towards Southbe #vecV_"south"=-9hatjm/s#

For 2nd 2s the displacement of the object towards Southbe #vecd_"south"=-9hatjm/sxx2s=-18hatjm#

Net displacement during t=(5+2)=7s is
#vecd_"net"=35hatjm-18hatjm=17hatjm->"towards north"#

Hence the Net Velocity
#vecV_"net"=vecd_"net"/t=17/7hatjm=2.43m/s->"towards north"#

Total distance covered during 7 s
#d_"total"=|vecd_"north"|+|vecd_"south"|=|35hatjm|+|-18hatjm|=53m#

Hence Average speed
#V_"avg" = d_"total"/t=53/7m/s~~7.6m/s #