Question

A car increases its speed with uniform rate from 20 km/h to 50 km/h in 10 seconds, average speed of car is

Answer 1

Step 1: Given

Initial velocity(u)=20 km/h= 20*$\frac{5}{18}$ m/s= 50/9 m/s

Final velocity(V)=50 km/h= 50*$\frac{5}{18}$ m/s= 125/9 m/s

Time(t)=10 sec

Let S is the distance covered and a is acceleration.

Step 2: Formula used

v=u+a*t (First equation of motion)

S = ut+$\frac{1}{2}$a$t^2$ (Second equation of motion)

Step 3: Finding total distance travelled

125/9 = 50/9 + a*10

a = 75/90 $\frac{m}{s^2}$

a= 0.833$\frac{m}{s^2}$

Now,

S = ut+$\frac{1}{2}$a$t^2$

S = $\frac{50}{9}$ *10+$\frac{1}{2}$ *0.833*100 m

S = 97.11 m

Hence, total distance covered is 97.11 m.

Step 4: Finding the average speed

Average speed = total distance/total time

Average speed = 97.11/10 m/s

Average speed = 9.71 m/s = 34.99 km/h.

Hence, average speed of car is 34.99 km/h.