Anonymous
Anonymous asked in Science & MathematicsPhysics · 7 months ago

# help in spring question physics?

A block of mass 1.5 kg is placed on a flat surface, and it is being pulled horizontally

by a spring with a spring constant 1.2 × 103 N/m  The coefficient

of static friction between the block and the table is µs = 0.60, and the coefficient of sliding

friction is µk = 0.40.

(a) By what amount must the spring be stretched to start the block moving?

(b) What is the acceleration of the block if the stretch of the spring is maintained at a constant value equal to that required to start the motion?

(c) By what amount must the spring be stretched to keep the mass moving at constant

speed?

Relevance

(a) To start the block moving, the static friction should be overcome

spring force = Static frictional force

kx = μ(s)N

kx = μ(s)mg

x = μ(s)mg/k

x = 0.60*1.5*9.8/(1.2 x 10³)

x = 0.00735 m or 7.35 mm

The block should be stretched just over 7.35 mm to start moving

(b) F(net) = Spring force - Kinetic frictional force

ma = kx - μ(k)N

ma = kx - μ(k)mg

a = kx/m - μ(k)g

a = (1.2 x 10³)*(0.00735)/1.5 - 0.40*9.8

a = 2.0 m/s²

(c) To keep constant speed, the net force on the block must be 0

F(net) = Spring force - Kinetic frictional force

0 = kx - μ(k)N

kx = μ(k)mg

x = μ(k)mg/k

x = 0.40*1.5*9.8/(1.2 x 10³)

x = 0.0049 m or 4.9 mm

The spring should be kept stretched by 4.9 mm to maintain constant speed.

• Login to reply the answers