In a crash test, a car of mass 1.41×10^3 kg collides with a wall and rebounds. The initial and final velocities of the car are vi=−15.4 m/s and vf=2.87 m/s, respectively. If the collision lasts for 0.154 s, find the following. a. The impulse delivered to the car due to the collision.
b. The size and direction of the average force exerted on the car (Indicate the direction with the sign of your answer.)
c. Suppose the car doesn't rebound off the wall, but the time interval of the collision remains at 0.158 s. In this case, the final velocity of the car is zero. Find the average force exerted on the car. (Indicate the direction with the sign of your answer.)

answer: the correct answer is 1.

explanation: there are various process in which a radioactive nuclei decays:

1) alpha decay: in this process, a heavier nuclei decays into lighter nuclei by releasing alpha particle. the mass number is reduced by 4 units.

2) electron capture: in this decay process, a parent nuclei absorbs an electron and gets converted into a neutron. simply, a proton and an electron combines together to form a neutron. mass number does not change in this process.

3) gamma ray emission: it is a decay process in which an unstable nuclei gives excess energy by a spontaneous electromagnetic process. this decay releases . this process does not change the mass number.

4) positron emission: it is a type of decay process, in which a proton gets converted to neutron and an electron neutrino. this is also known as -decay. in this the mass number remains same.

from the above information, we see that only alpha-decay is producing a change in the mass number of the nucleus.

kepler used the data from tycho blahe (his mentor) to construct the laws of planetary motion.

probably not if net force is zero