Question

shopper in a supermarket pushes a loaded cart with a horizontal force of 8 N. The cart has a mass of 26 kg.

(a) How far will it move in 2.0 s, starting from rest? (Ignore friction.)
1 m
(b) How far will it move in 2.0 s if the shopper places his 30 N child in the cart before he begins to push it?
2 m

Answer 1

Data:

Horizontal force, F =10 N

Mass of the cart, M = 26kg

Weight of the child, W = 30 N

Mass of the child, m = W / g

                                = 30 / 9.8

                                = 3.06 kg

Time, t = 2 s

Initial velocity of the cart, vi = 0 m/s

Solution:

(a)

Acceleration, a = Net force / Total mass [ From Newton's second law ]

                        = F / M

                        = 10 / 26

                        = 0.384 m/s^2

Distance, S = vi t + (1/2) a t^2

                  = 0 * 2 + [ 0.5 * 0.384 * 2^2 ]

                  = 0.77 m

Ans:

Distance moved, S = 0.77 m

(b)

Acceleration, a = Net force / Total mass [ From Newton's second law ]

                        = F / ( M + m )

                        = 10 / ( 26 + 3.06 )

                        = 0.344 m/s^2

Distance, S = vi t + (1/2) a t^2

                  = 0 * 2 + [ 0.5 * 0.344 * 2^2 ]

                  = 0.69 m

Ans:

Distance moved, S = 0.69 m