Question

A 15-kg block rests on a level frictionless surface and is attached by a light string to a 5.0-kg hanging
mass where the string passes over a massless frictionless pulley. If g = 9.8 m/s2, what is the tension
in the connecting string?

Answer 1

Mass of the block on the surface, m = 15 kg

Mass of the hanging mass, M = 5 kg

Acceleration due to gravity, g = 9.8 m/s^2

Let

Tension in the string = T

Equation for hanging mass :

M g - T = M a ...........(1)

Equation for mass on the surface:

T = m a ..................(2)

By adding (1) and (2)

M g = a ( M + m )

Acceleration, a = M g / ( M + m )

=5 * 9.8 / 20

=2.45 m/s^2

Hence, Tension in the string, T = m a

=15 * 2.45

=36.75 N

≈ 37 N