diff --git a/interface/src/avatar/AvatarMotionState.cpp b/interface/src/avatar/AvatarMotionState.cpp
index 4c5aaacb95..6fc1bd8196 100644
--- a/interface/src/avatar/AvatarMotionState.cpp
+++ b/interface/src/avatar/AvatarMotionState.cpp
@@ -21,6 +21,17 @@ AvatarMotionState::AvatarMotionState(AvatarSharedPointer avatar, const btCollisi
     _type = MOTIONSTATE_TYPE_AVATAR;
 }
 
+void AvatarMotionState::handleEasyChanges(uint32_t& flags) {
+    ObjectMotionState::handleEasyChanges(flags);
+    if (flags & Simulation::DIRTY_PHYSICS_ACTIVATION && !_body->isActive()) {
+        _body->activate();
+    }
+}
+
+bool AvatarMotionState::handleHardAndEasyChanges(uint32_t& flags, PhysicsEngine* engine) {
+    return ObjectMotionState::handleHardAndEasyChanges(flags, engine);
+}
+
 AvatarMotionState::~AvatarMotionState() {
     assert(_avatar);
     _avatar = nullptr;
@@ -46,6 +57,9 @@ PhysicsMotionType AvatarMotionState::computePhysicsMotionType() const {
 const btCollisionShape* AvatarMotionState::computeNewShape() {
     ShapeInfo shapeInfo;
     std::static_pointer_cast<Avatar>(_avatar)->computeShapeInfo(shapeInfo);
+    glm::vec3 halfExtents = shapeInfo.getHalfExtents();
+    halfExtents.y = 0.0f;
+    _diameter = 2.0f * glm::length(halfExtents);
     return getShapeManager()->getShape(shapeInfo);
 }
 
@@ -60,25 +74,31 @@ void AvatarMotionState::getWorldTransform(btTransform& worldTrans) const {
     worldTrans.setRotation(glmToBullet(getObjectRotation()));
     if (_body) {
         _body->setLinearVelocity(glmToBullet(getObjectLinearVelocity()));
-        _body->setAngularVelocity(glmToBullet(getObjectLinearVelocity()));
+        _body->setAngularVelocity(glmToBullet(getObjectAngularVelocity()));
     }
 }
 
 // virtual
 void AvatarMotionState::setWorldTransform(const btTransform& worldTrans) {
-    // HACK: The PhysicsEngine does not actually move OTHER avatars -- instead it slaves their local RigidBody to the transform
-    // as specified by a remote simulation.  However, to give the remote simulation time to respond to our own objects we tie
-    // the other avatar's body to its true position with a simple spring. This is a HACK that will have to be improved later.
     const float SPRING_TIMESCALE = 0.5f;
     float tau = PHYSICS_ENGINE_FIXED_SUBSTEP / SPRING_TIMESCALE;
     btVector3 currentPosition = worldTrans.getOrigin();
-    btVector3 targetPosition = glmToBullet(getObjectPosition());
-    btTransform newTransform;
-    newTransform.setOrigin((1.0f - tau) * currentPosition + tau * targetPosition);
-    newTransform.setRotation(glmToBullet(getObjectRotation()));
-    _body->setWorldTransform(newTransform);
-    _body->setLinearVelocity(glmToBullet(getObjectLinearVelocity()));
-    _body->setAngularVelocity(glmToBullet(getObjectLinearVelocity()));
+    btVector3 offsetToTarget = glmToBullet(getObjectPosition()) - currentPosition;
+    float distance = offsetToTarget.length();
+    if ((1.0f - tau) * distance > _diameter) {
+        // the avatar body is far from its target --> slam position
+        btTransform newTransform;
+        newTransform.setOrigin(currentPosition + offsetToTarget);
+        newTransform.setRotation(glmToBullet(getObjectRotation()));
+        _body->setWorldTransform(newTransform);
+        _body->setLinearVelocity(glmToBullet(getObjectLinearVelocity()));
+        _body->setAngularVelocity(glmToBullet(getObjectAngularVelocity()));
+    } else {
+        // the avatar body is near its target --> slam velocity
+        btVector3 velocity = glmToBullet(getObjectLinearVelocity()) + (1.0f / SPRING_TIMESCALE) * offsetToTarget;
+        _body->setLinearVelocity(velocity);
+        _body->setAngularVelocity(glmToBullet(getObjectAngularVelocity()));
+    }
 }
 
 // These pure virtual methods must be implemented for each MotionState type
@@ -145,3 +165,8 @@ void AvatarMotionState::computeCollisionGroupAndMask(int32_t& group, int32_t& ma
     mask = Physics::getDefaultCollisionMask(group);
 }
 
+// virtual
+float AvatarMotionState::getMass() const {
+    return std::static_pointer_cast<Avatar>(_avatar)->computeMass();
+}
+
diff --git a/interface/src/avatar/AvatarMotionState.h b/interface/src/avatar/AvatarMotionState.h
index 07e8102752..2738aba8ee 100644
--- a/interface/src/avatar/AvatarMotionState.h
+++ b/interface/src/avatar/AvatarMotionState.h
@@ -23,6 +23,9 @@ class AvatarMotionState : public ObjectMotionState {
 public:
     AvatarMotionState(AvatarSharedPointer avatar, const btCollisionShape* shape);
 
+    virtual void handleEasyChanges(uint32_t& flags) override;
+    virtual bool handleHardAndEasyChanges(uint32_t& flags, PhysicsEngine* engine) override;
+
     virtual PhysicsMotionType getMotionType() const override { return _motionType; }
 
     virtual uint32_t getIncomingDirtyFlags() override;
@@ -64,6 +67,8 @@ public:
 
     virtual void computeCollisionGroupAndMask(int32_t& group, int32_t& mask) const override;
 
+    virtual float getMass() const override;
+
     friend class AvatarManager;
     friend class Avatar;
 
@@ -76,6 +81,7 @@ protected:
     virtual const btCollisionShape* computeNewShape() override;
 
     AvatarSharedPointer _avatar;
+    float _diameter { 0.0f };
 
     uint32_t _dirtyFlags;
 };
diff --git a/libraries/avatars-renderer/src/avatars-renderer/Avatar.cpp b/libraries/avatars-renderer/src/avatars-renderer/Avatar.cpp
index 9682c81697..615f11e897 100644
--- a/libraries/avatars-renderer/src/avatars-renderer/Avatar.cpp
+++ b/libraries/avatars-renderer/src/avatars-renderer/Avatar.cpp
@@ -861,7 +861,6 @@ bool Avatar::shouldRenderHead(const RenderArgs* renderArgs) const {
     return true;
 }
 
-// virtual
 void Avatar::simulateAttachments(float deltaTime) {
     assert(_attachmentModels.size() == _attachmentModelsTexturesLoaded.size());
     PerformanceTimer perfTimer("attachments");
@@ -1544,12 +1543,13 @@ void Avatar::updateDisplayNameAlpha(bool showDisplayName) {
     }
 }
 
-// virtual
 void Avatar::computeShapeInfo(ShapeInfo& shapeInfo) {
     float uniformScale = getModelScale();
-    shapeInfo.setCapsuleY(uniformScale * _skeletonModel->getBoundingCapsuleRadius(),
-            0.5f * uniformScale *  _skeletonModel->getBoundingCapsuleHeight());
-    shapeInfo.setOffset(uniformScale * _skeletonModel->getBoundingCapsuleOffset());
+    float radius = glm::max(MIN_AVATAR_RADIUS, uniformScale * _skeletonModel->getBoundingCapsuleRadius());
+    float height = glm::max(MIN_AVATAR_HEIGHT, uniformScale *  _skeletonModel->getBoundingCapsuleHeight());
+    shapeInfo.setCapsuleY(radius, 0.5f * height);
+    glm::vec3 offset = uniformScale * _skeletonModel->getBoundingCapsuleOffset();
+    shapeInfo.setOffset(offset);
 }
 
 void Avatar::getCapsule(glm::vec3& start, glm::vec3& end, float& radius) {
@@ -1572,9 +1572,8 @@ float Avatar::computeMass() {
     return _density * TWO_PI * radius * radius * (glm::length(end - start) + 2.0f * radius / 3.0f);
 }
 
-// virtual
 void Avatar::rebuildCollisionShape() {
-    addPhysicsFlags(Simulation::DIRTY_SHAPE);
+    addPhysicsFlags(Simulation::DIRTY_SHAPE | Simulation::DIRTY_MASS);
 }
 
 void Avatar::setPhysicsCallback(AvatarPhysicsCallback cb) {
diff --git a/libraries/physics/src/ObjectMotionState.h b/libraries/physics/src/ObjectMotionState.h
index 0ca28d6b09..4a3b200559 100644
--- a/libraries/physics/src/ObjectMotionState.h
+++ b/libraries/physics/src/ObjectMotionState.h
@@ -110,8 +110,8 @@ public:
     MotionStateType getType() const { return _type; }
     virtual PhysicsMotionType getMotionType() const { return _motionType; }
 
-    void setMass(float mass);
-    float getMass() const;
+    virtual void setMass(float mass);
+    virtual float getMass() const;
 
     void setBodyLinearVelocity(const glm::vec3& velocity) const;
     void setBodyAngularVelocity(const glm::vec3& velocity) const;
diff --git a/libraries/physics/src/PhysicsEngine.cpp b/libraries/physics/src/PhysicsEngine.cpp
index ee87cab8e8..66a4edb486 100644
--- a/libraries/physics/src/PhysicsEngine.cpp
+++ b/libraries/physics/src/PhysicsEngine.cpp
@@ -105,9 +105,9 @@ void PhysicsEngine::addObjectToDynamicsWorld(ObjectMotionState* motionState) {
         }
         case MOTION_TYPE_DYNAMIC: {
             mass = motionState->getMass();
-            if (mass != mass || mass < 1.0f) {
-                qCDebug(physics) << "mass is too low, setting to 1.0 Kg --" << mass;
-                mass = 1.0f;
+            const float MIN_DYNAMIC_MASS = 0.01f;
+            if (mass != mass || mass < MIN_DYNAMIC_MASS) {
+                mass = MIN_DYNAMIC_MASS;
             }
             btCollisionShape* shape = const_cast<btCollisionShape*>(motionState->getShape());
             assert(shape);
diff --git a/libraries/shared/src/AvatarConstants.h b/libraries/shared/src/AvatarConstants.h
index e90e25d5b0..58cbff6669 100644
--- a/libraries/shared/src/AvatarConstants.h
+++ b/libraries/shared/src/AvatarConstants.h
@@ -69,6 +69,7 @@ static const float MIN_AVATAR_SCALE = 0.005f;
 
 static const float MAX_AVATAR_HEIGHT = 1000.0f * DEFAULT_AVATAR_HEIGHT; // meters
 static const float MIN_AVATAR_HEIGHT = 0.005f * DEFAULT_AVATAR_HEIGHT; // meters
+static const float MIN_AVATAR_RADIUS = 0.5f * MIN_AVATAR_HEIGHT;
 static const float AVATAR_WALK_SPEED_SCALAR = 1.0f;
 static const float AVATAR_SPRINT_SPEED_SCALAR = 3.0f;