A cart loaded with bricks has a total mass of 10.1 kg and is pulled at constant
ID: 1464640 • Letter: A
Question
A cart loaded with bricks has a total mass of 10.1 kg and is pulled at constant speed by a rope. The rope is inclined at 29.9 above the horizontal and the cart moves 8 m on a horizontal floor. The coefficient of kinetic friction between ground and cart is 0.7 .
The acceleration of gravity is 9.8 m/s2 .
1. What is the normal force exerted on the cart by the floor?
Answer in units of N.
2. How much work is done on the cart by the rope?
Answer in units of kJ.
3. Note: The energy change due to friction is a loss of energy.
What is the energy change Wf due to fric- tion?
Answer in units of kJ.
Explanation / Answer
1)
N = m*g*cos(theta)
= 10.1*9.8*cos(29.9)
= 85.8 N
2) Let F is the applied force, F = mue_K*N
= 0.7*85.8
= 60.06 N
Workdone by the rope = F*d
= 60.06*8
= 480.48 J
3) Here Workdone friction = -W_rope
= -80.48 J
so, energy change = -480.48 J
= -0.48 kJ (here negative sign indicates decrese in energy)
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