Projectile motion locust jump question

[The_big_dill]

Homework Statement

A Locust can jump as far as 75 cm horizontally, given a 55° angle above horizontal, what is the initial velocity?

Given:
d=75cm (0.75m)

Angle=55°

Homework Equations

a= v/t

d=vt

The Attempt at a Solution

t = (v)sin55 / 9.81

t = 0.75 / (v)cos55

t = t

(v)sin55 / 9.81 = 0.75 / (v)cos55

(cross multiply)

((v)sin55) ((v)cos55) = (9.81) (0.75)

v²(0.47) = 7.36

v = √ (7.36 / 0.47)

v = 4.0m/s

 

[The_big_dill]

Figured it out :)

The textbook (McGraw-Hill Physics 12) only introduced the formula which makes it VERY easy to solve this question in the next few pages.

Solution:

R = v²(sin²Ɵ) / 2 (g)

(Plug in given values and solve for unknown variable)

v = 2.8 m/s