Question

An electric toy car with a mass of `4 kg` is powered by a motor with a voltage of `7 V` and a current supply of `1 A`. How long will it take for the toy car to accelerate from rest to `3/2 m/s`?

Answer 1

`=9/14s`

Explanation:

Given

• `m->"Mass of toy car "=4kg`
• `V-> "Applied voltage "= 7V`
• `I-> "Current supply "=1A`
• `v-> "Velocity gained by toy car "= 3/2ms^-1`
• `"Let t be the time taken to gain the velocity " 3/2ms^-1 " from rest"`

Now assuming there is no loss of energy due to friction etc, we can apply conservation of energy to solve the problem.

`Now Power P = IxxV`

`"Electrical work done"="Gain in KE"`

`=>Pxxt=1/2xxmxxv^2`

`=>IxxVxxt=1/2xxmxxv^2`

`=>1xx7xxt=1/2xx4xx(3/2)^2`

`=>t =9/14s`