Question

1. There is a 10 kg textbook resting on a table (1m) above the ground, you want to raise the book 0.8m above that.
a. What is the change in potential energy to do so?
(I did w= 1.8*98?)
b. If you hold the book there (0.8 above the table) for 10m what is the work being done?
(I did w= 1.8*98*10?)


2. A puck is sliding on ice at velocity v, if another puck is added and sticks to the first puck what is that combined velocity?
(I got 2v?)


3. A plane is flying at v=300 km/h there is a wind from southwest at v= 60km/h. Find ground velocity of the plane.
(I did sqr ((300)^2+(60)^2))

4. A projectile is launched at v= 15m/s at an angle 60 above the horizontal.
a. What is the vertical velocity when it lands?
b. What is the acceleration halfway when projectile reaches max height?

Answer 1

1a.
PE change = PE2 - PE1 = Mgh2 - Mgh1 = (10*9.8*1.8) - (10*9.8*1.0) =

1b. W = F*d =(M*g) * d = (98) * 0.8 Joules.

3. What is the direction of the plane?

4. Vo = 15m/s[60o].
a. Xo = 15*Cos60 = 7.5 m/s = Hor. component of initial velocity.
Yo = 15*sin60 = 13.0m/s = Vertical component of initial velocity.

Y^2 = Yo^2 + 2g*h = 0.
13^2 + (-19.6)h = 0 ,
h = 8.62 m. = Max. ht.

Y^2 = Vo^2 + 2g*h = 0 + 19.6*8.62 = 169,
Y = 13m/s = Vertical velocity when it lands.

b. a = g = -9.8 m/s^2.