A raindrop has a mass of 9.0 × 107 kg and is falling near the surface of the earth. Calculate the magnitude of the gravitational force exerted (a) on the raindrop by the earth and (b) on the earth by the raindrop. (a) Fraindrop (b) Fearth = = i i

a bridge across a small stream is made by supporting a 10m long log with a mass of 75kg with ropes tied at the ends of the log to the tree on the banks. the rope on the right makes a 25 degree angle with the ground. the rope on the left makes a 20 degree angle with the ground. a 25kg child us standing 7.5 m from the left bank. write the net force equation for the y direction. write the net force equation for the x direction. write the torque equation (use the left end of the log as the axis of rotation).

A block is placed on a wooden plank, which is initially horizontal.  One end of the plank is slowly raised to make it more and more inclined, and for a while the block stays in place on the plank and doesn't slide due to static friction.  Finally, when the plank reaches an incline of 56.3oabove horizontal, the block begins to slide.  What is the  coefficient of static friction between the block and the plank?

The 3500-lb automobile shown in the picture is traveling down the 10-degree inclined road at a speed of 20 ft/s. If the driver wishes to stop the car, determine how far s the tires skid on the road if the brakes are jammed, causing the wheels to lock. Coefficient of kinetic friction between wheels and road is 0.5.

On a test flight a rocket with mass 400 kg blasts off from the surface of the earth. The rocket engines apply a constant upward force F until the rocket reaches a height of 100 m and then they shut off. A) If the rocket is to reach a maximum height of 400 mm above the surface of the earth, what value of F is required? Assume the change in the rocket's mass is negligible. (Express your answer with the appropriate units.)

A loaded grocery cart is rolling across a parking lot in a strong wind. You apply a constant force F = (27 N) - (38 N) to the cart as it undergoes a displacement s(-8.5 m)i (3.0 m)j.

A contestant in a winter sporting event pushes a 49 kg block of ice at an angle 25∘ below the positive direction across a frozen lake, as shown in the figure. Assume the coefficients of static and kinetic friction are μs=0.1 and μk=0.03Calculate the minimum force Fmin he must exert to get the block sliding across the ice in newtons.  What is its acceleration in meters per second squared once it starts to move, if that minimum force is maintained?

Fy m +x P On the left a mass, 17.9 kg, is at rest. Force Pis acting on the mass in the (Fx) direction as shown. The coefficient of static friction between the mass and the surface is μ = 0.855. The coefficient of kinetic friction between the mass and the surface is µ = 0.565. What is the greatest force P that can be applied and the mass will remain at rest?

You are trying to slide a sofa across a horizontal floor. The mass of the sofa is 2.0 x 102kg, and you need to exert a force of 3.5 x 102N to make it just begin to move. (a) Calculate the coefficient of static friction between the floor and the sofa.(b) After it starts moving, the sofa reaches a speed of 2.0 m/s after 5.0 s. Calculate the coefficient of kinetic friction between the sofa and the floor.

Kinesiologists—scientists who study human motion—can measure the forces that act on runners as they round a curve. The forces on a runner’s feet are a vertical normal force that, on average, serves to counteract gravity, and a static friction force parallel to the ground and pointing toward the center of the runner’s circular path. The average value of this inward-pointing force is measured to be 600 N for a 75 kg runner rounding a curve that has a 2.5 m radius. What is this runner’s speed?