Calculate the magnitude of the normal force on a 12.7 kg block in the following circumstances. (Enter your answers in N.)   (a) The block is resting on a level surface. N   (b) The block is resting on a surface tilted up at a 20.8° angle with respect to the horizontal. N   (c) The block is resting on the floor of an elevator that is accelerating upward at 2.28 m/s2. N (d) The block is on a level surface and a force of 165 N is exerted on it at an angle of 20.8° below the horizontal. N

A car moving at 30 m/s crashes into a tree and stops in 0.3 s. Calculate the force the seat belt exerts on a passenger in the car to bring him to a halt. The mass of the passenger is 84 kg. (Enter the magnitude.) N

Block A has a mass of 3 kg and block B has a mass of 4.8 kg. They are in contact and slide over a frictionless horizontal surface. A force of 19 N acts on B as shown. F Find: mb a) the acceleration; m/s² b) the force on B due to A; N c) the net force on B; N ma d) the force on B due to A if the blocks are interchanged. N

A rocket takes off from Earth's surface, accelerating straight up at 37.2 m/s2. Calculate the normal force (in N) acting on an astronaut of mass 81.4 kg, including his space suit. (Assume the rocket's initial motion parallel to the +y-direction. Indicate the direction with the sign of your answer.)    ?N

Especially part C

A rocket takes off from Earth's surface, accelerating straight up at 45.2m/s2. Calculate the normal force (in N) acting on an astronaut of mass 85.9kg, including his space suit. (Assume the rocket's initial motion parallel to the +y-direction. Indicate the direction with the sign of your answer.) N

An object of mass 0.77 kg is initially at rest. When a force acts on it for 2.9 ms it acquires a speed of 12.7 m/s. Find the magnitude (in N) of the average force acting on the object during the 2.9 ms time interval. (Enter a number.) N

A block whose weight is 40 N rests on a horizontal surface. The coefficient of static friction between the block and the surface is 0.50. A string is attached to the block. The string is pulled horizontally with a force of 15 N. Which one of the following statements is correct? O The magnitude of the force of friction on the block is 20 N. O The magnitude of the force of friction on the block is 15 N. O The force of friction cannot be determined because the coefficient of kinetic friction is not given. O The force of friction cannot be determined because the normal force of the surface on the block is not known. O The magnitude of the force of friction on the block is 5 N.

A 2.50-kg object is moving in a plane, with its x and y coordinates given by x = 6t² - 2 and y = 5t³ + 1, where x and y are in meters and t is in seconds. Find the magnitude of the net force acting on this object at t = 1.60 s. N

A cardboard box rests on the floor of an elevator. The box has a mass m = 2.75 kg and the elevator has an upward acceleration of a.   a.  Write an expression for the sum of the forces acting on the box in the y-direction, ΣFy, given that up is the positive y-direction. Your answer should be in terms of FN, m, and g.  b. Write an expression for the normal force, FN, that the block experiences in terms of the elevator's acceleration, the block's mass, and the acceleration of gravity.  c.  If the elevator's acceleration has a magnitude of g in the downward direction, what would the normal force, FN1 be in Newtons?  d.If the elevator's acceleration had a magnitude of g in the upward direction, what would the normal force FN2 be in Newtons?