Question

A constant net force of 20 n is applied to a 32 kg car, causing it to speed up from 4. 0 to 9. 0 m/s. how long is the force applied?

Answer 1

Given :-

• Constant force, F = 20 N
• Mass of Car = 32 kg
• Initial speed, u = 4 m/s
• Final Speed = 9 m/s

To Find:-

• Duration for which force is appiled

Solution:-

`\green{ \underline { \boxed{ \sf{Force,F= Mass * Acceleration }}}}`

So,

`\sf Acceleration,a = (Force)/(Mass)`

`\sf \implies (20)/(32)`

`\implies (5)/(8) m/s^2`

Now,

By first equation of motion -

`\green{ \underline { \boxed{ \sf{v-u=at}}}}`

So,

`\sf t = (v-u)/(a)`

where

• v = final velocity
• u = initial velocity
• a = acceleration
• t = time duration

Putting Values -

`\sf t = (9-4)/( (5)/(8))`

`\sf t = (5)/( (5)/(8))`

`\sf t = \cancel5 * \frac{8}{\cancel{5}}`

`\sf t = 8 \:seconds`

>>>Therefore, Force is applied for 8 seconds.