Question

A car advertisement states that a certain car can accelerate from rest to 70 km/h in 7
seconds. Find the car’s acceleration. Hint: Convert time in hours so that all units are
same.

Answer 1

Explanation:

V =70 km/ h

u = 0 km /h

t =, 7 sec

Acceleration = V - u/t

= 70-0/7

= 70/ 7

= 10km/h^2 ans.

Answer 2

Acceleration

According to the information given,

initial velocity(u) $=0$ ( as car starts  from rest)

final velocity(v)  $= 70 \ km/h$

time taken(t)  $= 7 seconds$

Changing the unit of final velocity in m/s we get,

$70 km/hr=\frac{70\times 1000}{60\times 60}=\frac{175}{9}m/s$

Using equation of motion,

$v=u+at$

$\frac{175}{9}=0+a\times7\\ \\\implies \frac{175}{9} =7a\\\\\implies 2.77 \ m/sec^2$

Hence, required acceleration is 2.77 m/s².