4 Newton's Laws of Motion - BC Science Physics 11

4.2 Review Questions
1. What unbalanced force is needed to accelerate a
5.0 kg cart at 5.0 m/s 2 ?
2. A net force of 7.5 × 10 4 N acts on a spacecraft of
mass 3.0 × 10 4 kg.
(a) At what rate will the spacecraft accelerate?
(b) Assuming constant acceleration is maintained,
how fast will the spacecraft be moving after 25 s,
if its initial speed was 5.0 × 10 3 m/s?
3. A model rocket has a mass of 0.12 kg. It accelerates
vertically to 60.0 m/s in 1.2 s.
(a) What is its average acceleration?
(b) What is the unbalanced force on the rocket?
(c) If the force of gravity on the rocket is 1.2 N,
what is the total thrust of its engine?
4. What is the mass of a rock if a force of 2.4 × 10 3 N
makes it accelerate at a rate of 4.0 × 10 1 m/s 2 ?
5. A fully loaded military rocket has a mass of
3.0 × 10 6 kg, and the force of gravity on it at ground
level is 2.9 × 10 7 N.
(a) At what rate will the rocket accelerate during
lift-off, if the engines provide a thrust of
3.3 × 10 7 N?
(b) Why will this acceleration not remain constant?
6. A boy and his skateboard have a combined mass of
60.0 kg. After an initial shove, the boy starts coasting
at 5.5 m/s along a level driveway. Friction brings
him to rest in 5.0 s. The combined force of gravity on
the boy and skateboard is 5.9 × 10 2 N. What is the
average coefficient of rolling friction between the
driveway and the skateboard wheels?
© Edvantage Interactive 2012 ISBN 978-0-9864778-3-6 Chapter 4 Newton’s Laws of Motion 115