Liftoff Energy
Speed, height, and power physics help?
A 2kg toy rocket blasts straight up from the ground level with a kinetic energy of 40J. At the exact top of its trajectory its total mechanical energy is 140J. Disregard air resistance.
1. What is its speed at liftoff?
2. What maximum height does it reach?
3. If it took 30 seconds to reach the top, how much power did the engine produce after liftoff?
How do I solve these questions?
1. KE + PE = constant mechanical energy
at the top of its flight, KE=0 therefore PE = 140 J
at liftoff, PE = 0, therefore KE = 140 J
KE = 1/2 mv^2
140 J = 1/2 ( 2 kg) v^2
v^2 = 140 m^2/s^2
v= 11.83 m/s
2. max h?
PE = mgh
140 J = (2kg) (9.8 kg m/s^2) (h)
h = 7.14 m
3. P = ME / t
P = 140 J / 30 s
P = 6.47 watts
 |
| Herbalife Liftoff Energy boosting tablets energize yourself redbull replace | |
 |
$16.00 Time Remaining: 3h 4m Buy It Now for only: $18.00 Buy It Now | Bid now | Add to watch list |
| HerbaLife Energy Drink Tablets LIFT OFF | |
 |
$13.99 Time Remaining: 1d 2h 3m |
| Herbalife Heart Health Energy Fitness Item | |
 |
$14.99 Time Remaining: 2d 5h 17m Buy It Now for only: $14.99 Buy It Now | Add to watch list |
| Energy tablets DissolvableLiftOff | |
 |
$11.50 Time Remaining: 3d 21h 7m |
| 5 BOXES OF HERBALIFE LIFT OFF ENERGY DRINK TABLETS | |
 |
$70.00 Time Remaining: 4d 21h 47m Buy It Now for only: $70.00 Buy It Now | Add to watch list |
| Herbalife Products weight management programs enhancers and energy fitness | |
 |
$17.60 Time Remaining: 5d 1h 49m Buy It Now for only: $17.60 Buy It Now | Add to watch list |
| NEW Herbalife Liftoff Energy Drink 4 Different Flavors 10 Tablets per Box | |
 |
$14.96 Time Remaining: 12d 20h 5m Buy It Now for only: $14.96 Buy It Now | Add to watch list |
| 2 HERBALIFE LIFTOFF LIFT OFF IGNITE ME ORANGE EFFERVESCENT ENERGY DRINK BOX LOT | |
 |
$24.99 Time Remaining: 16d 3h 28m Buy It Now for only: $24.99 Buy It Now | Add to watch list |
| Energy High Hi Lift Off Road Jack Handle Polyurethane Isolator Anti Rattle Black | |
 |
$13.99 Time Remaining: 18d 6h 7m Buy It Now for only: $13.99 Buy It Now | Add to watch list |
| Energy High Hi Lift Off Road Jack Handle Polyurethane Isolator Anti Rattle Red | |
 |
$13.99 Time Remaining: 18d 6h 7m Buy It Now for only: $13.99 Buy It Now | Add to watch list |
| HERBALIFE LIFTOFF IGNITE ME ORANGE EFFERVESCENT ENERGY SUPPLEMENT 10 Tablets | |
 |
$19.99 Time Remaining: 18d 6h 27m Buy It Now for only: $19.99 Buy It Now | Add to watch list |
| Lift off energy drink tabs | |
 |
$50.00 Time Remaining: 26d 1h 1m Buy It Now for only: $50.00 Buy It Now | Add to watch list |
| Liftoff Effervescent Energy Supplement 25 OFF | |
 |
$13.00 Time Remaining: 28d 14h 23m Buy It Now for only: $13.00 Buy It Now | Add to watch list |
| 3 HERBALIFE LIFTOFF LIFT OFF IGNITE ME ORANGE EFFERVESCENT ENERGY DRINK BOX LOT | |
 |
$35.99 Time Remaining: 28d 14h 48m Buy It Now for only: $35.99 Buy It Now | Add to watch list |
| HERBALIFE LIFTOFF LIFT OFF ORANGE ENERGY DRINK EFFERVESCENT TABLETS BOX NEW | |
 |
$13.99 Time Remaining: 29d 12h 57m Buy It Now for only: $13.99 Buy It Now | Add to watch list |