1. Rocket Problems Answers
1. A 1000-kg rocket is on a launch pad.
(a) What is the weight of the rocket?
Wt. = m g
= ( 1000 kg )( 9.8 m/s2 )
Wt. = N
m = 1000 kg
Wt.
= N

2. 1. A 1000-kg rocket is on a launch pad.
(b) How much thrusting force from the engines is necessary for the
rocket to simply hover above the pad?
FA = ?
To hover, FA must match the weight
so FA = N
m = 1000 kg
Wt.
= N

3. 1. A 1000-kg rocket is on a launch pad.
(c) How much additional force is necessary to accelerate the rocket
upwards at 7.5 m/s2 ?
FA = ?
Fnet = m a
a = 7.5 m/s2
= ( 1000 kg )( 7.5 m/s2 )
Fnet
Fnet = N
m = 1000 kg
Wt.
= 9800 N

4. 1. A 1000-kg rocket is on a launch pad.
(d) How much total force is exerted by the engines?
FA = ?
Fnet = FA + Wt.
a = 7.5 m/s2
= FA + ( )
Fnet = N
m = 1000 kg
FA = N
Wt.
= N

5. 2. A rocket of mass 750 kg has engines that exert a total thrusting
force of 2.0 x 104 N.
(a) How much force from the engines must be used to overcome the
weight of the rocket?
FA = N
Wt. = m g
= ( 750 kg )( 9.8 m/s2 )
Wt. = N
m = 750 kg
so FA = N
Wt.
= 7350 N

6. 2. A rocket of mass 750 kg has engines that exert a total thrusting
force of 2.0 x 104 N.
(b) What is the net upward force on the rocket?
FA = N
Fnet = FA + Wt.
Fnet = ( ) + ( )
Fnet
Fnet = N
m = 750 kg
Wt.
= N

7. 2. A rocket of mass 750 kg has engines that exert a total thrusting
force of 2.0 x 104 N.
(c) What is the acceleration of the rocket?
Fnet = m a
FA = N
m m
a = ?
Fnet
Fnet = N
a = m
m = 750 kg N =
750 kg
Wt.
= N
a = 17 m/s2

8. 3. A rocket of mass 450 kg takes off and accelerates at 12.0 m/s2.
Determine the total thrusting force from the engines.
Wt. = m g
= ( 450 kg )( 9.8 m/s2 )
= N
FA = ?
a = 12 m/s2
Fnet = m a
= ( 450 kg )( 12 m/s2 )
= N
Fnet
= N
m = 450 kg
Fnet = FA + Wt.
N = FA + ( N )
N N
Wt.
= 4410 N
FA = N

9. 4. A rocket of mass 1500 kg has engines that exert a total thrusting
force of 5.0 x 104 N. Find the upward acceleration of the rocket.
Wt. = m g
= ( 1500 kg )( 9.8 m/s2 )
= N
FA = N
Fnet = FA + Wt.
a = ?
= ( N ) + ( N )
Fnet
= N
= N
m = 1500 kg
Fnet = m a
m m
Fnet N
Wt.
= N
a = = m
1500 kg
a = 24 m/s2