Calculating Initial Speed and Velocity of Thrown Keys

[cbrowne]

Homework Statement

A man standing on the sidewalk throws a set of keys vertically upward to his
wife in the window of their apartment 4.0 m above. The wife catches the keys
1.5 s later. (a) With what initial speed were the keys thrown? (b) What is the
velocity of the keys just before they were caught? (c) Draw a diagram showing
the trajectory of the keys.

The Attempt at a Solution

d= 4.0 m
Δt= 1.5 s
g= -9.8 m/s^2

Δd= ViΔt+1/2aΔt

-ViΔt= 1/2 at2-Δd

-Vi= 1/2 at2- Δd /Δt

-Vi= -10.016 m/s

ANSWER FOR A ->>Vi= 10.016 m/s

b) V_f= Vi+at

Vf= (110.016 m/s)-(9.8)(1.5)= (-4.684m/s)

ANSWER FOR B >> -4.684 m/s

 

[alphysicist]

Hi cbrowne,

Homework Statement

A man standing on the sidewalk throws a set of keys vertically upward to his
wife in the window of their apartment 4.0 m above. The wife catches the keys
1.5 s later. (a) With what initial speed were the keys thrown? (b) What is the
velocity of the keys just before they were caught? (c) Draw a diagram showing
the trajectory of the keys.

The Attempt at a Solution

d= 4.0 m
Δt= 1.5 s
g= -9.8 m/s^2

Δd= ViΔt+1/2aΔt

-ViΔt= 1/2 at2-Δd

-Vi= 1/2 at2- Δd /Δt

-Vi= -10.016 m/s

ANSWER FOR A ->>Vi= 10.016 m/s

b) V_f= Vi+at

Vf= (110.016 m/s)-(9.8)(1.5)= (-4.684m/s)

ANSWER FOR B >> -4.684 m/s

Your answers look right to me.

 

[rl.bhat]

Your answers are correct.