Question

A box is sliding along a frictionless surface and gets to a ramp. Disregarding friction, how fast should the box be going on the ground in order to slide up the ramp to a height of 2.5 meters, where it stops? (Use g = 9.8 m/s2.)
A) 2.2 m/s
B) 7.0 m/s
C) 9.9 m/s
D) 24 m/s

Answer 1

This is amazing.  When you read the quest ion, you wouldn't think there's enough information there to find an answer.  But there is !

-- When the block is sliding along the flat surface, its kinetic energy is (1/2)(Mass·v²).

-- When it's 2.5m up the ramp and stops, its potential energy is (2.5m)·(Mass·g).

-- If there's no friction anywhere, these energies are equal.

(1/2)(Mass·v²)  =  (2.5m)·(Mass·g)

(v²/2) = (2.5m) · g

v² = 5m · g

v² = 49 m²/s²

v = 7 m/s  (B)

Answer 2

Answer:

B: 7.0 m/s

Explanation:

on edge