To lift a 1200 N motorcycle a vertical height of 1.3 m onto a pickup truck, a...

Question

To lift a 1200 N motorcycle a vertical height of 1.3 m onto a pickup truck, a motocross rider pushes the bike up a ramp 2.4 m, requiring an effort force up the ramp of 820 N. What is the efficiency of the ramp?

Answer: 79%

Answer 1

A straight vertical lift of 1200 Newtons through a distance of 1.3 meters equates to work of

(1200 × 1.3) or 1560 Newton-Dot-Meters or 1560 Joules.

A push up the ramp of 820 Newtons through a distance of 2.4 meters equates to work of

(820 × 2.4) or 1968 Newton-Dot-Meters or 1968 Joules.

The ramp method requires 1560 Joules of work as well as an additional (1968 − 1560) or

408 Joules.

The efficiency of the ramp is then stated as 1560/1968 or 0.7926829268 (roughly 79.27%)

since the cyclist in the ramp method does 100% of the work demanded by a straight vertical lift

plus an additional 408 Joules out of the 1968 Total-Ramp-Joules (or 0.2073170732 ≈ 20.73%) .