12.6 CHAPTER 12. FORCE,MOMENTUM AND IMPULSE
M
F 2
θ
F 1 =Mg
How is the body affected when the angle θ is increased?
(a) It remains at rest.
(b) It lifts up off the surface, and accelerates towards the right.
(c) It lifts up off the surface, and accelerates towards the left.
(d) It accelerates to theleft, moving along the smooth horizontal surface.
- [IEB 2003/11 HG1]Which of the followingstatements correctly explains why a pas-
senger in a car, who isnot restrained by the seat belt, continues to move forward
when the brakes are applied suddenly?
(a) The braking force applied to the car exerts an equal and opposite force on the
passenger.
(b) A forward force (called inertia) acts on the passenger.
(c) A resultant forward force acts on the passenger.
(d) A zero resultant force acts on the passenger.
- [IEB 2004/11 HG1]
A rocket (mass 20 000 kg) accelerates from rest to 40 m·s−^1 in the first 1,6 seconds of
its journey upwards intospace.
The rocket’s propulsionsystem consists of exhaust gases, which are pushed out of an
outlet at its base.
(a) Explain, with reference to the appropriatelaw of Newton, how the escaping
exhaust gases exert an upwards force (thrust) onthe rocket.
(b) What is the magnitude of the total thrust exerted on the rocket during the first
1,6 s?
(c) An astronaut of mass80 kg is carried in the space capsule. Determinethe resul-
tant force acting on himduring the first 1,6 s.
(d) Explain why the astronaut, seated in his chair, feels “heavier” whilethe rocket is
launched.
- [IEB 2003/11 HG1- Sports Car]
(a) State Newton’s Second Law of Motion.
(b) A sports car (mass1 000 kg) is able to accelerate uniformly fromrest to 30
m·s−^1 in a minimum time of 6s.
i. Calculate the magnitude of the acceleration of the car.
ii. What is the magnitude of the resultant forceacting on the car duringthese
6 s?
(c) The magnitude of the force that the wheels of the vehicle exerton the road
surface as it acceleratesis 7500 N. What is the magnitude of the retardingforces
acting on this car?
(d) By reference to a suitable Law of Motion, explain why a headrest is important in
a car with such a rapid acceleration.
- [IEB 2005/11 HG1]A child (mass 18 kg) isstrapped in his car seatas the car moves
to the right at constantvelocity along a straightlevel road. A tool boxrests on the
seat beside him.
