Gravity Questions

Question 1

Given that the time the object takes to hit the ground is 1.01s. What is the velocity of the object at the moment of impact?

S = 5m

Answer 1

Add v-u/t into our equation s = ut + 1/2at²

So s = ut + 1/2 (v-u/t)t²

Then apply u = 0 so 2s/t = v

So v = 2 × 5/1.01 so v = 9.9ms^-1

Question 2

The goal keeper kicks the ball at an angle of 30° from the horizontal and at a velocity of 5ms^-1. Assuming the balls travels in a straight line. What are the d and y componants of the balls velocity

If the balls velocity decreases to 3ms^-1 and the y componant increase to 4ms^-1 and the velocity remains unchanged, what are the x and y componts of the balls velocity?

Answer 2

n = sinØvi/sinØvr

x = 5cos(30l
x = 4.33ms^-1

y = 5sin(30)
y = 2.5ms^-1

avy = a cos (Ø)
3 = 5cos(Ø)
3/5 = cos (Ø)
Ö = cos^-1 (3/5)
Ø = 53°

avy = a sin (Ø)
4 = 5sin(Ø)
4/5 = sin(Ø)
Ø = sin^-1 (4/5)
Ø = 53°

Question 3

A object is dropped out of a 5m window. For how long will it fall?

Answer 3

s = ut + 1/2at²
s = 1/2at² (re-arrange)

t = √2s/a
t = √2x5/9.8
t = 1.01s

Question 4

Show that when the same object takes 2 seconds to hit the ground, the height of the window is not 10m

Answer 4

s = 1/2 x 9.8 x 2²
s = 19.6m

Question 5

If the object takes 1.01s to hit the floor, what is the velocity of the object at the moment of inpact?

Answer 5

s = ut + 1/2at²
s = ut + 1/2(v-u/t)t² (Simplify and u = 0)

v = 2s/t
v = 2x5/1.01
v = 9.9ms^-1

Question 6

If the object takes 1.01s to hit the floor, what is the velocity of the object at the moment of inpact? (Alternate method)

Answer 6

v = √2as
v = √2 x 9.8 x 5
v = 9.9ms^-1

Arguably a better because we are not relying on previously worked out values. It is also faster.