H 6.1 2/2 points (graded) Suppose you have a 150-kg wooden crate resting on a wood floor, with coefficients of static and sliding friction between these wood surfaces 0.500 and 0.300 respectively. a. What maximum force (in N) can you exert horizontally on the crate without moving it? Give your answer to two significant figures without units. 735 correct b. If you continue to exert this force once the crate starts to slip, what will its acceleration ( in ) then be? Give your answer to two significant figures without units. 1.96 correct H 6.2 2/2 points (graded) A machine at a post office sends packages out a chute and down a ramp to be loaded into delivery vehicles. You can neglect air resistance in both parts. a. Calculate the acceleration ( in ) of a box heading down a 10° slope, assuming the coefficient of friction for a parcel on waxed wood is 0.100. Give your answer to two significant figures without units. 0.74 correct b. Find the angle (in degrees) of the slope down which this box could move at a constant velocity. Give your answer to two significant figures without units. 5.71 correct H 6.3 2/2 points (graded) A 30.0-g ball at the end of a string is swung in a vertical circle with a radius of 25.0 cm. The tangential velocity is 200.0 cm/s. Find the tension in the string in Newtons :
a. at the top of the circle. Enter your answer to three significant figures without unit. 0.186 correct b. at the bottom of the circle. Enter your answer to three significant figures without unit. 0.774 correct H 6.4 2/2 points (graded) If a car takes a banked curve at less than the ideal speed, friction is needed to keep it from sliding toward the inside of the curve (a problem on icy mountain roads). a. Calculate the ideal speed ( in ) to take a 120 m radius curve banked at 15.0°. Give your answer to two significant figures without units. 17.75 correct b. What is the minimum coefficient of friction needed for a frightened driver to take the same curve at 20.0 km/h? Give your answer to three significant figures without units. 0.24 correct H 6.5 3/3 points (graded) A child of mass 40.0 kg is in a roller coaster car that travels in a loop of radius 7.00 m. At point A the speed of the car is 10.0 m/s, and at point B, the speed is 10.5 m/s. Assume the child is not holding on and does not wear a seat belt.
A B 1 1 30° a. What is the force (in N) of the car seat on the child at point A? Enter your answer to two significant figures without unit. 179 correct b. What is the force (in N) of the car seat on the child at point B? Enter your answer to two significant figures without unit. 290 correct c. What minimum speed (in m/s) is