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Transcript
1. The diagram shows a boy pushing a box in a warehouse. A force of 10 N is required to overcome friction between the box and the floor. Any extra force applied to the box makes the box accelerate. (a) If the boy pushes with a force of 30 N: (i) Draw on the diagram the two horizontal forces acting on the block [2] (ii) Calculate the resultant force acting on the box. _______________________________________________________ _______________________________________________________ ____________________________________________________ [1] (iii) Write down a formula which links mass, acceleration and resultant force. _______________________________________________________ ____________________________________________________ [1] (iv) Calculate the acceleration of the box. _______________________________________________________ _______________________________________________________ _______________________________________________________ ____________________________________________________ [2] (b) As the box increases in speed the friction force also increases. Eventually the friction force balances the push force exerted by the boy. (i) What is the size of the friction force now? ___________________________________________________ [1] (ii) What is the size of the resultant force? ___________________________________________________ [1] (iii) Describe the motion of the box. ______________________________________________________ ___________________________________________________ [1] (c) Suggest a way of reducing the friction between the box and the floor. ______________________________________________________________ ___________________________________________________________ [1] (d) Not all the energy is transferred to the box. Into what other forms is this energy converted? ___________________________________________________________ [1] 2. (a) Name two vertical forces acting on a raindrop falling through the air. ______________________________________________________________ ___________________________________________________________ [2] (b) Explain why the raindrop eventually moves with constant velocity towards the ground. ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ___________________________________________________________ [2] 3. A rocket of mass 100 kg has two forces acting on it as it moves vertically upward just after lift off; its own weight force and the thrust of the rocket engines, which is 3000N. (a) Draw a diagram showing the two forces acting on the rocket. (b) Use the value of the mass to calculate the weight of the rocket. ______________________________________________________________ ___________________________________________________________ [1] (c) At take off calculate the resultant force acting on the rocket. ______________________________________________________________ ______________________________________________________________ ___________________________________________________________ [2] (b) Use the equation for Newton’s second law to calculate the initial acceleration of the rocket at take off. ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ___________________________________________________________[2] 4. An electric motor is used to lift a bag of cement of weight 200N through a vertical distance of 5 metres. (a) Write down, in words, the equation linking force, distance and work done. ______________________________________ ____________________________________ [1] (b) Calculate the work done in lifting the cement. ______________________________________________________________ ______________________________________________________________ ___________________________________________________________ [2] (c) The motor supplied 10,000 J of energy in the lifting of the cement. 5. (i) How much energy was wasted or not usefully transferred? _____________________________________________________ __________________________________________________ [1] (ii) State and explain what has happened to the wasted energy during the transfer. _____________________________________________________ _____________________________________________________ __________________________________________________ [2] 6. A type of toy catapult consists of a movable plunger attached to a spring. The handle was pulled down to fully compress the spring and then released. The ball of mass 0.1 kg was projected 0.75 m vertically into the air. (Take g=10N/kg) (a) Describe the energy changes that take place when the handle is released. ______________________________________ ______________________________________ ___________________________________ [3] (b) Calculate the maximum gravitational potential energy gained by the ball. (Write down any formula that you use and show your calculations) ______________________________________________________________ ______________________________________________________________ ___________________________________________________________ [3] (c) Use the concept of energy transfer to calculate the speed of the ball as it left the plunger. ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ___________________________________________________________ [3]