Refer to the 2th Law of Newton
F = m. a
F = 15 x 2.8 = 42 N
Answer:

Explanation:
given,
de broglie wavelength of the particle = 2.1 × 10⁻¹⁰m
Kinetic energy increase factor = 3
de broglie wavelength of new particle = ?
we know,

Kinetic energy

...........(1)
Kinetic energy of other particle
............(2)
dividing equation (1)/(2)




Answer: 180N/m(to 2 significant figures)
Explanation:
According to hooked law which states that the extension of a material is directly proportional to the applied force provided that the elastic limit is not exceeded. Mathematically, F = ke where;
F is the applied force in newtons
k is the elastic/spring constant in N/m
e is the extension in meters
Given applied force = 35N
extension = 20cm = 0.2m
Since F = ke,
k = F/e = 35/0.2
k = 175N/m
The spring constant is 175N/m
= 180N/m (to 2significant figures)