1. The problem statement, all variables and given/known data
A student throws a set of keys vertically upward to his fraternity brother, who is in a window a distance h above. The brother's outstretched hands catches the keys on their way up at a time t later. (a) With what initial velocity were the keys thrown? (b) What was the velocity of the keys just before they were caught?
A student throws a set of keys vertically upward to his fraternity brother, who is in a window a distance h above. The brother's outstretched hands catches the keys on their way up at a time t later. (a) With what initial velocity were the keys thrown? (b) What was the velocity of the keys just before they were caught? (Answer should be in terms of h, t, and g.)
2. Relevant equations
[itex]\Delta[/itex]x = v0t + (1/2)at2
v2 = v02 + 2a[itex]\Delta[/itex]x
3. The attempt at a solution
Question 1: when did the act of throwing begin? When the keys were released from the hand, or during the wind up of the arm/hand, before releasing the keys? The physics tutor in the math lab told me the initial velocity was 0. But that is not true if at the moment of release the keys were already at a higher velocity.
Question 2: What does "[a]nswer should be in terms of h, t, and g" mean? Do they want actual number using h, t, and g, or is this a numberless problem?
a) [itex]\Delta[/itex]x = vot + (1/2)at2
v0 = (1/t)([itex]\Delta[/itex]x - (1/2)at2)
v0 = (1/t)(h - (1/2)gt2)
v0 = (h/t) - ((gt)/2)
b) v2 = v02 + 2a[itex]\Delta[/itex]x
v2 = ((h/t) - (gt)/2)2 + 2gh
v = ((h/t) - (gt)/2) + 2gh
Thanks for any help!)
A student throws a set of keys vertically upward to his fraternity brother, who is in a window a distance h above. The brother's outstretched hands catches the keys on their way up at a time t later. (a) With what initial velocity were the keys thrown? (b) What was the velocity of the keys just before they were caught?
A student throws a set of keys vertically upward to his fraternity brother, who is in a window a distance h above. The brother's outstretched hands catches the keys on their way up at a time t later. (a) With what initial velocity were the keys thrown? (b) What was the velocity of the keys just before they were caught? (Answer should be in terms of h, t, and g.)
2. Relevant equations
[itex]\Delta[/itex]x = v0t + (1/2)at2
v2 = v02 + 2a[itex]\Delta[/itex]x
3. The attempt at a solution
Question 1: when did the act of throwing begin? When the keys were released from the hand, or during the wind up of the arm/hand, before releasing the keys? The physics tutor in the math lab told me the initial velocity was 0. But that is not true if at the moment of release the keys were already at a higher velocity.
Question 2: What does "[a]nswer should be in terms of h, t, and g" mean? Do they want actual number using h, t, and g, or is this a numberless problem?
a) [itex]\Delta[/itex]x = vot + (1/2)at2
v0 = (1/t)([itex]\Delta[/itex]x - (1/2)at2)
v0 = (1/t)(h - (1/2)gt2)
v0 = (h/t) - ((gt)/2)
b) v2 = v02 + 2a[itex]\Delta[/itex]x
v2 = ((h/t) - (gt)/2)2 + 2gh
v = ((h/t) - (gt)/2) + 2gh
Thanks for any help!)
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