Abstract: An acceleration sensor for vehicle-sensitive systems is mounted on a part connected to the vehicle and comprises a mounting part having a baseplate, which has a spherical socket-shaped recess and bearing means for an impulse lever, which between the tip thereof and the part thereof mounted in the bearing means is enlarged to form a spherical socket-shaped cap. A ball which constitutes an inertia mass is provided between the cap and the socket-shaped recess and an actuating member, which preferably consists of a control pawl which is in contact, or almost in contact, with the tip of the impulse lever and is activated by the tip thereof as the ball is moved out of its position of rest by accelerations having predetermined values. The mounting part is directly or indirectly pivoted to a pivoted part of the vehicle, such as a seat or the rest of a seat, on an axis which extends through the region in which the tip of the impulse lever contacts the actuating member.