1) A steel ball of mass 5.2 g is fired vertically DOWNWARD from a height hof 18 m with an initial speed v0 of 14 m/s into a sandbed. It buries itself to a depth of 21 cm in the sand on impact. a) What is the work done by the sand on the steel ball? b) What was the average force exerted by the sand on the ball?

A 7.80-g bullet moving at 690 m/s penetrates a tree trunk to a depth of 5.10 cm. (a) Use work and energy considerations to find the average frictional force that stops the bullet.N(b) Assuming the frictional force is constant, determine how much time elapses between the moment the bullet enters the tree and the moment it stops moving.s

1. Boxing gloves are padded to lessen the force of a blow. The glove and face compress 7.5000 cm during a blow in which the 7.0000-kg arm and glove are brought to rest from an initial speed of 10.0000 m/s. ▬▬ - Think & Prepare 1. Make note of what's given and what's unknown. Relate known quantities to symbols. 2. Draw a labeled sketch if possible. 3. Identify the physics principle and approach. Write down relevant equations symbolically. Simplify if possible. 4. Insert numerical quantities to solve for unknowns. 5. Does the answer make sense? % (a) Calculate the change in kinetic energy of the glove and arm. AKE = (b) Where does this energy go? O Search 5 O into doing work against the force exerted by the face against the glove O into doing work against gravity O into the potential energy of the face O into the potential energy of the glove and arm T 4- 6 Y 17 + & J 7 90 8 * 8 U I 이 144 ( 9 110 DII O E DDI I P 2 { 4 ( ← backs

An 7.6 kgkg crate is pulled 5.4 mm up a 30∘∘ incline by a rope angled 19 ∘ above the incline. The tension in the rope is 140 NN and the crate's coefficient of kinetic friction on the incline is 0.23.How much work is done by tension, by gravity, and by the normal force?What is the increase in thermal energy of the crate and incline?

% Consider a situation where you carry a 20-N box up a flight of stairs, raising its elevation by 5 m. 5 The work you do is 4 J. 15 True O False O Bi 89 6 X 7 18 ASUS 8 A 19 9 f10 fll f12 pau bre

i) A small 25g toy rocket is launched straight up from the ground at 144 km/h (a) What is the  kinetic energy of the toy rocket? (b) Find the work done by gravity after it has risen 220 m. (i) (a). The kinetic energy of the toy rocket is = (b). The work done by gravity after it has risen 220 m is =

An object is displaced by 0.5m against a force of friction at 2N. What is the work done on the object by the friction? -6J 1J -1J 4J

202.) The forces exerted by a rubber shock absorber varies with the displacement as shown. Estimate the work done to the ball shown after it has displaced the shock absorber 8.0 cm. Has the ball gained or lost energy? O Work Rubber Shock Absorber Force (Newtons) Clearly indicate how you make your estimate. Work 1.7NM Has the ball gained or lost energy? 40 30 20 10 4 8 10 Displacement (cm)

(2) The combined force of lift and thrust on a model airplane is a constant F = (4î + 3j + 6k) N. a. How much work is done by the force F if the displacement of the airplane is: A = (6î – 5j – 3k) m? %3D b. Will this force cause the airplane to speed up, slow down or maintain a constant speed?

A crane at a construction site lifts a concrete block with a mass of m = 482 kg from the ground to the top of a building with a height of h = 23.9 m. How much work did the motor of the crane do? (Assume zero energy loss in the lifting mechanism due to friction.) -112894 J moter If the duration of the lift was 1.35 minutes, then what was the average power performed by the crane?