A large block that can move along a straight track has a mass of 60.0 kg and an

Question

A large block that can move along a straight track has a mass of 60.0 kg and an initial velocity of 1.40 m/s in the negative x-direction. The cart is then subjected to a net force that is initially in the positive x-direction, but which then switches direction to the negative x-direction at t = 20 s, as shown in the graph below.

(a) Find the momentum of the cart at t = 15 s. Don't forget to use a minus sign, if the momentum is in the negative direction.

b) Find the momentum of the cart at t = 25 s. Don't forget to use a minus sign, if the momentum is in the negative direction.

Explanation / Answer

According to Newton's second law,

Force = change in momentum with time.

F = dp/dt

p2-p1 = F*dt (from 0 to 15 s)

=F*[t ]015since F is contant.

=20*(15-0)

=300 Ns.

Here p1=intial momentum = m*v =-60*1.4 =-84 Ns (since intial velocity v is in negative direction)

P2 = -84 Ns

P1= 300-84

=216 Ns

(b)

we need to calculate the momentum in two parts, first until 20 s. Second until 25 seconds

Momentu @ t=20m second

P20=20*20 - 84

=316 Ns

Momentum @ t=25 second

P25-P20 =-F*t =-10*5 -50

P25 = 266 Ns

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.