6. Use your knowledge of one Newton's laws of motion to explain how a creature or vehicle can use friction to speed up. You can explain using an example or using general ideas.

1. Pushing a Bor Two workers are sliding a 300 kg crate across the floor. One worker pushes forward on the crate with a force of 380 N while the other pulls in the same direction with a force of 350 N using a rope connected to the crate. Both forces are horizontal, and the crate slides with a constant speed. What is the crate's coefficient of kinetic friction on the floor? 2. Fun Friction Problem A 4000 kg truck is parked on a 7.0 slope. Calculate the frictional force on the truck. 3. Rolling Friction The rolling resistance for steel on steel is a paltry = 0.002. How long would it take a 500,000 kg train to come to a stop if it was originally rolling at 10 m/s?

7. You put a box on a skateboard and give it a quick push with a certain force. It starts to move. After it leaves your hand, it will... * a. Continue at a constant speed forever. O b. Slow down constantly until it stops. c. Speed up constantly forever. d. Speed up for a little while, then go at a constant speed forever. e. Speed up for a little while, go at a constant speed for a while, then slow down to a stop. sheet of oa

A blue car’s engine exerts a 1000 N force on the car.  A green car’s engine exerts a 500 N force on the car.  Both cars have the same mass.  If both cars start from rest, how will their times to reach 60 mph compare?  Assume they experience the same amount of air resistance. A not enough information  B both cars will take the same time to reach 60 mph. C green car takes less time to reach 60 mph  D blue car takes less time to reach 60 mph

7. A car of mass m, is speeding up on level ground with an acceleration as a function of time given by d(t) = a1 where az and t, are non-zero constants. The mass of the car stays the same (it is a constant). a. Write Newton's 2nd Law for a system that only includes the car. b. Integrate your Newton's 2nd Law equation with respect to time fromt = 0 to t = 2t1 to determine an expression that relates the impulse exerted on the car to the mass and acceleration of the car. c. Determine the magnitude of the impulse on the car from t = 0 to t = 2t1. Note: this is the vector sum of all the impulses or "net impulse" acting on the car during this time period.

1. You are working as a letter sorter in the Post Office. Postal regulations require that employees' footwear must have a minimum coefficient of static friction of 0.5 on a specified tile surface. You are wearing athletic shoes for which you do not know the coefficient of static friction. In order to determine the coefficient, you imagine that there is an emergency and start running across the room. You have a co-worker time you, and find that you can begin at rest and move 4.23 m in 1.20 s. If you try to move faster than this, your feet slip. Assuming your acceleration is constant, does your footwear qualify for the postal regulation? 7

2. A 3.00 kg block is placed at the top of a 21.0° rough inclined plane with us = 0.325 and Hk =0 .215 %3D and a length of 1.78 m. a) Draw a free-body diagram of the block. b) Prove that, if released from rest, the block will immediately start sliding. c) Find the magnitude of the block's acceleration. d) Calculate the time the block takes to reach the end of the incline.

A box is being pulled to the right over a rough surface. T> fk, so the box is speeding up. Suddenly the rope breaks. What happens? The box Select one: a. Slows steadily until it stops b. Continues with the speed it had when the rope broke С. Continues speeding up for a short while, then slows and stops. O d. Keeps its speed for a short while, then slows and stops. e. Stops immediately

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A yoyo of radius R and mass M is released from rest with the string vertical and its top end fixed up a support as shown below. How fast is the center of mass of the yoyo moving when it has fallen a distance of 47 cm. Ignore the mass of the string and express your answer if m/s