Sunday

December 28, 2014

December 28, 2014

Posted by **jeff** on Wednesday, August 29, 2007 at 4:00pm.

I used the following formula, but was informed my answer was wrong.

100m + (t) 65km/hr = 0 + (t)78km/hr

and solved for (t).

t = 100m / (78km/hr - 65km/hr)

I converted km/hr to m/sec and did the math and got

t = 100m / (21.668 m/sec - 18.057 m/sec)

t = 100m / 3.611 m/sec

t = 27.693 seconds

What did I do Wrong?

- physics- what did i do wrong -
**bobpursley**, Wednesday, August 29, 2007 at 4:25pmThe only thing I see is significant digits. There is no way you can have the answer in five sig digits, given the input data.

- physics- what did i do wrong -
**DrBob222**, Wednesday, August 29, 2007 at 4:40pmIf you leave it in hr, the time for the car to catch the bus is 0.00769 hours.

The bus will travel 0.00769*65 = 0.5 km

The car will travel 0.00769*78 = 0.6 km

The difference is 0.1 km which is the 100 meter separation at th beginning. So the answer MUST be right, at least worked the right way, but the teacher may object to the digits. Perhaps 28 seconds?

**Answer this Question**

**Related Questions**

Physics - A car and a bus are moving down a hill, the bus is 3X heavier than the...

Algebra! Help needed! - I'm having a little trouble with this problem... Please ...

physics - Just as a car starts to accelerate from rest with an acceleration of 1...

physics - At the instant a traffic light turns green, a car starts from rest ...

physics - At the instant a traffic light turns green, a car starts from rest ...

math - the distance between town A and town B was 210km. At 9:20pm a bus sets ...

math - distance = rate x time or d = r*t car traveling 40 mi/hr goes 40 mi/hr x ...

physics - A bus and a car have an inelastic head-on collision. The bus has a ...

physics - A bus and a car have an inelastic head-on collision. The bus has a ...

Algebra continued - A car trveling at 88km/h. If the bus has a 1.5h head start, ...