Question

Could someone please check over my answers? I'm not very good at physics, and therefore am not sure if I got all of them correct.

1. A skier of mass 70.0 kg is pulled up a slope by a motor-driven cable. How much work is required to pull the skier 60.0 m up a 350 slope (ignore friction) at a constant 2.0 m/s?
a) 2.4 * 10^4 J //my answer//
b) 5.6 * 10^3 J
c) 8.2 * 10^4 J


2. The kinetic energy of an object can be negative. The gravitational potential energy associated with an object can be negative.
a) No to both. //my answer//
b) No and yes.
c) Yes to both.
d) Yes and no.


3. How long does it take a 19 kW steam engine to do 6.8 * 10^7 J of work?
a) 1 hr //my answer//
b) 30 min
c) 300 s
d) 2 hr


4. If you dropped a ball off a cliff, how far below the ledge will it have fallen in 2 seconds?
a) about 20 m
b) about 15 m //my answer//
c) about 100 m
d) about 10 m


5. Two years equals approximately how many seconds?
a) 1.26 * 10^8 s
b) 3.2 * 10^7 s //my answer//
c) 6.3 * 10^6 s
d) 6.3 * 10^7 s


6. The displacement of an airplane from its starting point is 200 km at 60 degrees NE. Its easterly component is:
a) 200 km
b) 100 km
c) 173.2 km //my answer//


7. A projectile is shot an angle into the air. Neglecting air resistance,


It's horizontal acceleration is
a) 9.8 m/s^2
b) 0.0 m/s^2
c) 10 m/s //my answer//


It's downward acceleration is
a) 9.8 m/s^2 //my answer//
b) 0.0 m/s^2
c) 10 m/s


It's vertical acceleration is
a) 9.8 m/s^2
b) 0.0 m/s^2 //my answer//
c) 10 m/s

Answer 1

1. M = 70 kg.
Slope = 35o?
L = 60 m.

h = 60*sin35 = 34.4 m.

Work = F*h = Mg*h = 70*9.8 * 34.4 = 23,608 J.

3. 19kW = 19kJ/s. = 19,000 J/s
6.8*10^7J * 1s./ 1.9*10^4J = 3580 s. =
0.994 h. or 1 h.

4. d = 0.5g*t^2

5. 24h/day * 365days/yr. * 3600s./h =

6. 200km[60o] N. of E.
Dx = 200*Cos60 = 100 km.

7. Incomplete.