Question

A ball is thrown downwards with speed 5m/s from a top a 20m high building.
a. How long does it take for the ball to hit the ground?
b. How fast is it moving when it hits the ground?

Answer 1

(a) S=u t+(1/2) gt^2

20=5 t+(1/2) (9.8) t^2

t=1.57 second

(b) V=u+gt

=5+(9.8)(1.57)

=20.42m/s

Answer 2

thnks

Answer 3

what are the variables S , u

Answer 4

S is distance travelled
u is initial velocity
v is final velocity

Answer 5

there is 1 more equation for this

v^2=u^2+ 2as

Answer 6

so which one should i use

Answer 7

All you can use depend on the situation.
In this situation ,
S,u,g is given, you decide what to use :)

Answer 8

ok thnkds a lot

Answer 9

im still confused as to calculating the first part the units are messing me up and also you have t and t^2

Answer 10

use SI unit m, m/s , s , m/s^2

t^2 and t use quadratic equation to solve you get 1 negative(rejected) 1 positive(1.57)