# Tutor profile: Erich M.

## Questions

### Subject: Physics

A ball is thrown horizontally with a speed of 25 m/s from the top of a tower 20 meters high. Assuming level ground below and negligible air resistance, what will be the magnitude of the vertical velocity component when the ball hits the ground? A. 25 m/s B. 15 m/s C. 20 m/s D. 50 m/s E. 10 m/s

In physics problems, it is often good to figure out what the question wants to know, and then apply our knowledge to help us arrive at the solution. This problem wants to know the magnitude of the vertical velocity of an object after it falls a certain distance. Next, it is helpful to figure out the givens, or what we know from reading the problem. These are : The initial velocity is horizontal The initial velocity is 25 m/s The height is 20 m There is no air resistance With the assumption of no air resistance, we can safely use the kinematic equations for projectile motion. We want to pick one that includes the things we know, and only one that we don't. This leads us to see there is one equation that fits perfectly, being: Vf ^ 2 = Vi ^ 2 + 2 * a * d We know Vi is zero in the vertical direction initially, so Vi = 0 We know d = 20 We know a = g = 9.8 m/s ^2 So if we plug in these knows into our equation, we get: Vf ^ 2 = 0 ^ 2 + 2 * 9.8 * 20 Vf ^ 2 = 0 + 392 Vf = sqrt( 392) Vf = 19.8 Looking at the answers, we see that the closest answer to 19.8 is 20, so C is the correct answer.

### Subject: GRE

In a class of 32 students 75 per cent are girls. 50 per cent of the students study French. The number of girls who study French || 7 A. The quantity on the left is greater B. The quantity on the right is greater C. Both are equal D. The relationship cannot be determined without further information

We first need to determine the number of girls and boys in the class # of girls = .75 * 32 = 24 # of boys = .25 * 32 = 8 Since 50% of students study French, that means .5 * 32 = 16 So 16 students study French. We are concerned with how many girls possibly study French. If the maximum number of boys study French, 8, that leaves 8 girls who study French. Since no more boys could possibly study French, we know that at least 8 girls study French, and 8 > 7, so the answer is : A

### Subject: Mechanical Engineering

The strain placed on a material is represented as e, and the stress represented as s. If e= 0.635 and s= 127E6 Pa, calculate the Young's modulus of the material, and identify the material.

We know that s=E * e, so E = s / e Therefore E = 127E6 / 0.635 E = 200E9 Pa <------------ ANSWER Looking this up on a table corresponds to steel. <--------ANSWER

## Contact tutor

needs and Erich will reply soon.