91影视

The sled dog in the figure drags sleds A and B across the snow. The coefficient of friction between the sleds and the snow is $0.10.$If the tension in rope $1$is$150N,$what is the tension in rope $2?$

Blocks A and B in the figure are connected by a massless string over a massless, frictionless pulley. The blocks have just been released from rest. Will the pulley rotate clockwise, counterclockwise, or not at all? Explain.

In case a, in the figure block A is accelerated across a frictionless table by a hanging $10N$weight $(1.02kg)$. In case b, block A is accelerated across a frictionless table by a steady $10N$tension in the string. The string is massless, and the pulley is massless and frictionless. Is A鈥檚 acceleration in case b greater than, less than, or equal to its acceleration in case a? Explain.

Two-thirds of the weight of a $1500kg$ car rests on the drive wheels. What is the maximum acceleration of this car on a concrete surface?

$FIGUREEX7.16$shows two $1.0kg$blocks connected by a rope. A second rope hangs beneath the lower block. Both ropes have a mass of $250g$. The entire assembly is accelerated upward at $3.0m/s^2$by force $\stackrel{鈫�}{F}$

a. What is F?

b. What is the tension at the top end of rope $1$?

c. What is the tension at the bottom end of rope $1$?

d. What is the tension at the top end of rope $2$?

What is the tension in the rope of FIGURE EX7.17?

A $2.0$-m-long, $500g$rope pulls a $10kg$ block of ice across a horizontal, frictionless surface. The block accelerates at $2.0m/s^2$ . How much force pulls forward on (a) the ice, (b) the rope? Assume that the rope is perfectly horizontal.

A woman living in a third-story apartment is moving out. Rather than carrying everything down the stairs, she decides to pack her belongings into crates, attach a frictionless pulley to her balcony railing, and lower the crates by rope. How hard must she pull on the horizontal end of the rope to lower a $25kg$crate at steady speed?

A weightlifter stands up at constant speed from a squatting position while holding a heavy barbell across his shoulders.

a. Draw an interaction diagram.

b. Identify the 鈥渟ystem鈥� on your interaction diagram.

c. Draw a free-body diagram for each object in the system. Use

dashed lines to connect members of an action/reaction pair.

How does a sprinter sprint? What is the forward force on a sprinter as she accelerates? Where does that force come from? Your explanation should include an interaction diagram and a free-body diagram.