9.2.2 Speed and Acceleration, PT3 Focus Practice

Question 4:
Table below shows the distances travelled and the average speeds for four vehicles.

Vehicle	Distance (km)	Average speed (km/h)
A	230	115
B	250	100
C	170	85
D	245	70

Which vehicles took the same time to complete the journey?

Solution:
$$ Time taken for vehicle A= 230 115 =2 hours Time taken for vehicle B= 250 100 =2 1 2  hours Time taken for vehicle C= 170 85 =2 hours Time taken for vehicle D= 245 60 =3 1 2  hours

Thus, the vehicles A and C took the same time to complete the journey.

Question 5:
Mei Ling drives her car from Kuantan to Kuala Terengganu for a distance of 170 km for 2 hours. She then continues her journey to Kota Bahru and increases her speed to 100 kmh^-1 for 45 minutes.

Calculate the acceleration, in kmh^-2, of the car.

Solution:
$$ Speed from Kuantan to Kuala Terengganu = 170 2 =85  kmh −1 Acceleration = Final speed−Initial speed Time taken = 100−85 45 60 =20  kmh −2

Question 6:
Diagram shows the distance between K and L.

A car moves from K to L with an average speed of 80 kmh^-1. After rest for 1 hour 30 minutes, the car then returns to K. The average speed of the car from L to K increases 20%. If the car reaches K at 5 p.m., calculate the time the car starts its journey from K.


Solution: 
$$ The time taken from K to L = 160 80 =2 hrs The average speed from L to K =80×1.2 =96  kmh −1 The time taken from L to K = 160 96 =1 2 3  hrs The total time taken for the whole journey =2+1 1 2 +1 2 3 =5 1 6  hrs =5 hour 10 minutes



The car starts its journey from K at 11:50 a.m.