Question

From (v-t) diagram find (1) Distance travelled in 10 second.
(2) Total distance travelled in 50 second.
(3) Retardation

Answer 1

We know that the area under v-t graph gives the distance travelled 
DISTANCE TRAVELLED IN 0 TO 10 sec = A(△OAB) 

=`1/2` x OA x AB
= `1/2` x 10 x 10
= 50 m

DISTANCE TRAVELLED IN 0 TO 50 sec = A(Trapezium OBDE)
= `1/2` x (OE+BD) x AB
= `1/2` x (50+10) x 10
= 300 m
CONSIDER THE MOTION FROM 20 sec TO 50 sec
We know that slope of v-t graph gives acceleration
E=(50,0) and D=(20,10)
Slope of line DE=`(0-10)/(50-20)` = `-1/3` = -0.3333 m/s²

Distance travelled by object in 10 sec = 50 m
Distance travelled by object in 50 sec = 300 m
Acceleration = - 0.3333 m/s2